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Cyclopedia 

of 

Civil   Engineering 


A   General  Reference  Work  on 


SURVEYING,  HIGHWAY  CONSTRUCTION,  RAILROAD  ENGINEERING,   EARTHWORK, 

STEEL  CONSTRUCTION,  SPECIFICATIONS,  CONTRACTS,  BRIDGE  ENGINEERING, 

MASONRY    AND     REINFORCED     CONCRETE,    MUNICIPAL    ENGINEERING, 

HYDRAULIC    ENGINEERING,     RIVER    AND    HARBOR   IMPROVEMENT, 

IRRIGATION     ENGINEERING,      COST     ANALYSIS,       ETC. 


Prepared  by  a   Corps  of 


CIVIL    AND    CONSULTING   ENGINEERS   AND   TECHNICAL   EXPERTS   OF   THE 
HIGHEST   PROFESSIONAL   STANDING 


Illustrated  ivith  over  Two   Thousand  Engravings 


NINE  VOLUMES 


AMERICAN  TECHNICAL  SOCIETY 
CHICAGO 

1920 


COPYRIGHT,  1908,  1909,  1915,  1916,  1920 
BY 
AMERICAN  TECHNICAL  SOCIETY 


Copyrighted  in  Great  Britain 
All  Rights  Reserved 


Authors  and  Collaborators 


FREDERICK  E.  TURNEAURE,   C.   E.,  Dr.   Eng. 

Dean  of  the  Collo^e  of  Engineering,  and  Professor  of  Engineering,  Univer- 
sity  of   Wisconsin 

Memlier,   American    Society   of   Civil   Engineers 

Joint  Author  of  "Principles  of  Reinforced  Concrete  Construction,"  "Public 
Water   Supplies,"   etc. 


FRANK  O.  DUFOUR,  C.  E. 

With  Stone  and  Webster,  Boston,   Massachusetts 

Formerly    Structural    Engineer   with    Interstate   Commerce   Commission 

Formerly  Assistant  Professor  of  Structural  Engineering,  University  of  Illinois 

Member,  American  .Society  of  Civil   Engineers 

Member,  American  Society  for  Testing  Materials 


WALTER  LORING  WEBB,  C.  E. 

Consulting  Civil  En-gineer 

Member,   American    Society    of   Civil   Engineers 

Author    of    "Railroad    Construction,"    "Economics    of    Railroad    Construction, 
etc. 


W.  G.  BLIGH 

Inspecting  Engineer  of  Irrigation   Works,   Department  of   Interior,   Canada 
Formerly   in   Engineering  Service  of  His   Majesty   in   India 
Member,   Institute   Civil    Engineers    (London) 
Member,  American    Society   of   Civil   Engineers 
Member,  Canadian    Society   of   Civil   Engineers 


ADOLPH  BLACK,  C.  E. 

Civil  and   Sanitary  Engineer,   General   Chemical   Company,   Nev/   York  City 
Formerly  Adjunct  Professor  of  Civil  Engineering,   Columbia  University 


EDWARD   R.    MAURER,   B.   C.   E. 

Professor  of  Mechanics,   University   of   Wisconsin 

Joint  Author  of  "Principles  of  Reinforced   Concrete  Construction' 


AUSTIN  T.  BYRNE 

Civil  Engineer 

Author   of    "Highway    Construction,"    "Materials    and    Workmanship' 


jj€^nL>^ 


Authors  and  Collaborators— Continued 


A.  MARSTON,  C.  E. 

Dean   of   Division    of   Engineering   and    Professor   of    Civil    Engineering,    Iowa 

State  College 
Member,  American    Societj'    of   Civil   Engineers 
Member,  Western  Society  of  Civil  Engineers 


De  WITT  V.  MOORE 

Consulting  Engineer  and  Architect 

Formerly    District    Engineer-:— Central    District    Division    of    Valuation 

Interstate  Commerce  Commission,    Chicago 

Member,  American   Society    of   Engineering  Contractors 

Member,  Indiana  Engineering  Society 


W.   HERBERT  GIBSON,  B.  S.,  C.  E. 

Civil  Engineer 

Designer  of  Reinforced   Concrete 


JAMES  K.  FINCH.  C.  E. 


Associate  Professor  of  Civil  Engineering,  and  Director  of  Summer  School  of 
Surveying,    Columbia  University,   Now   York 


HENRY   J.   BURT,   B.    S.,    C.   E. 

General   Manager  for  Ilolabird   and   Roche,   Architects 

Member,   American   Society   of  Civil    Engineers 

Member,   Western   Society   of   Civil   Engineers 

Member,  Society    for   the   Promotion    of  Engineering   Education 


RICHARD  I.  D.  ASHBRIDGE 

Civil  Engineer 

Member,  American  Society  of  Civil   Engineers 


HERMAN  K.  HIGGINS 

Civil  Engineer 

Associate  Member,  American    Society   of  Civil   Engineers 

Member,  Boston    Society    of   Civil    Engineers 

Member,  New    England    Water   Works    Association 

MemlK'r,    American    Railway   P.ridge    and   lUiilding    Association 


ALFRED  E.  PHILLIPS,  C.  E.,   Ph.  D. 

Professor  of  Civil  Engineering,   Armour   Institute  of  Technology 


Authors  and  Collaborators — Continued 


H.   E.   MURDOCK,   M.   E.,    C.   E. 

Head    of    Department    of    Agricultural    Engineering,    Montana    State    College, 

Bozeman,  Montana 
Formerly    Irrigation   Engineer,   U.    S.   Department    of   Agriculture 


A.  B.  McDANIEL,  B.  S. 

Formerly   Assistant  Professor  of  Civil   Engineering,   University   of   Illinois 

Member,  American    Society    of   Civil   Engineers 

Member,   Society    for    the    Promotion    of   Engineering    Education 

Fellow,    Association    for   the  Advancement   of   Science 

Author  of   "Excavating   Machinery" 


GLENN  M.  HOBBS,  Ph.  D. 

Secretary  and  Educational  Director,  American  School  of   Correspondence 
Formerly    Instructor,    Department   of   Physics,   University    of   Chicago 
American  Physical  Society 


THOMAS   FLEMING,   Jr.,   B.    S.,   C.   E. 

With  Chester  &  Fleming,   Hydraulic  and   Sanitary   Engineers 
Associate   Member,   American    Society   of'  Civil    Engineers 
Memlier,  New   England   Water   Works   Association 
Member,  Engineers'    Society   of   Pennsylvania 


CHARLES    E.    MORRISON,    C.    E.,    Ph.    D. 

Formerly  Instructor  in  Civil  Engineering,  Columbia  University 

As.sociate   Member,   American    Society   of   Civil    Engineers 

Author   of   "Highway   Engineering,"    "High   Masonry    Dam    Design" 


EDWARD  B.  WAITE 

Formerly  Dean,  and  Head,   Consulting  Department,  American  School  of  Cor- 
respondence 
American    Society   of   Mechanical   Engineers 
Boston   Society  of  Civil  Engineers 


C.  A.  MILLER,  Jr. 

Associate  Editor,   American   Technical    Society 
Affiliated   Member,   Western   Society   of  Engineers 
Member,  American    Association    of    Engineers 
Member,  Illinois  Society  of  Architects 


JESSIE  M.  SHEPHERD,  A.  B. 

Head,    Publication   Department,   American    Technical    Society 


Authorities  Consulted 


THE  editors  have  freely  consulted  the  standard  technical  literature  of 
America  and  Europe  in  the  preparation  of  these  volumes.  They  de- 
sire to  express  their  indebtedness,  particularly,  to  the  following 
eminent  authorities,  whose  well-known  treatises  should  be  in  the  library  of 
everyone  interested  in  Civil  Engineering. 

Grateful  acknowledgment  is  here  made  also  for  the  invaluable  co- 
operation of  the  foremost  Civil,  Structural,  Railroad,  Hydraulic,  and  Sanitary 
Engineers  and  Manufacturers  in  making  these  volumes  thoroughly  repre- 
sentative of  the  very  best  and  latest  practice  in  every  branch  of  the  broad 
field  of  Civil  Engineering. 


WILLIAM  G.  RAYMOND,  C.  E. 

Dean  of  the  School  of  Applied  Science  and  Professor  of  Civil  Engineering  in  the  State 

University  of  Iowa;  American  Society  of  Civil  Engineers 
Author  of  "A  Textbook  of  Plane  Surveying,"  "The  Elements  of  Railroad  Engineering" 


JOSEPH  P.  FRIZELL 

Hydraulic  Engineer  and  Water-Power  Expert;  American  Society  of  Civil  Engineers 
Author  of  "Water  Power,  the  Development  and  Application  of  the  Energy  of  Flowing 
Water" 


FREDERICK  E.  TURNEAURE,  C.  E.,  Dr.  Eng. 

Dean  of  the  College  of  Engineering  and  Professor  of    Engineering,    University  of 

Wisconsin 
Joint  Author  of  "Public  Water  Supplies,"  "Theory  and  Practice  of  Modern  Framed 

Structures,"  "Principles  of  Reinforced  Concrete  Construction" 


HENRY  N.  OGDEN,  C.  E. 

Professor  of  Sanitary  Engineering,  Cornell  University 
Author  of  "Sewer  Design" 

DANIEL  CARHART,  C.  E. 

Emeritus  Professor  of  Civil  Engineering,  University  of  Pittsburgh 
Author  of  "Treatise  on  Plane  Surveying" 


HALBERT  P.  GILLETTE 

Editor  of  Engineering  and  Contracting;  American  Society  of  Civil  Engineers;  Formerly 

Chief  Engineer,  Washington  State  Railroad  Commission 
Author  of  "Handbook  of  Cost  Data  for  Contractors  and  Engineers" 


CHARLES  E.  GREENE,  A.  M.,  C.  E. 

Late  Professor  of  Civil  Engineering,  University  of  Michigan 

Author  of  "Trusses  and  Arches,  Graphic  Method,"  "Structural  Mechanics' 


Authorities  Consulted— Continued 


A.  PRESCOTT  FOLWELL 

Editor  of  Municipal  Journal  and  Engineer;  Formerly  Professor  of  Municipal  Engineer- 
ing, Lafayette  College 
Author  of  "Water  Supply  Engineering."  "Sewerage" 


IRVING  P.  CHURCH,  C.  E. 

Professor  of  Applied  Mechanics  and  Hydraulics.  Cornell  University 
Author  of  "Mechanics  of  Engineering" 


PAUL  C.  NUGENT,  A.  M.,  C.  E. 

Professor  of  Civil  Engineering,  Syracuse  University 
Author  of  "Plane  Surveying" 


FRANK  W.  SKINNER,  C.  E. 

Consulting  Engineer;  Associate  Editor  of  The  Engineering  Record 
Author  of  "Types  and  Details  of  Bridge  Construction" 


HANBURY  BROWN,  K.  C.  M.  G. 

Member  of  the  Institution  of  Civil  Engineers 
Author  of  "Irrigation,  Its  Principles  and  Practice" 

SANFORD  E.  THOMPSON,  S.  B.,  C.  E. 

American  Society  of  Civil  Engineers 

Joint  Author  of  "A  Treatise  on  Concrete,  Plain  and  Reinforced' 


JOSEPH  KENDALL  FREITAG,  B.  S.,  C.  E. 

American  Society  of  Civil  Engineers 

Author  of  "Architectural  Engineering,"  "Fireproofing  of  Steel  Buildings,"  "Fire  Pre- 
vention and  Fire  Protection" 


AUSTIN  T.  BYRNE,  C.  E. 

Civil  Engineer 

Author  of  "Highway  Construction,"  "Inspection  of  Materials  and  Workmanship  Em- 
ployed in  Construction" 


JOHN  F.  HAYFORD,  C.  E. 

Expert  Computer  and  Geodesist,  U.  S.  Coast  and  Geodetic  Survey 
Author  of  "A  Textbook  of  Geodetic  Astronomy" 


WALTER  LORING  WEBB,  C.  E. 

Consulting  Civil  Engineer;  American  Society  of  Civil  Engineers 

Author  of  "Railroad  Construction  in  Theory  and  Practice,"  "Economics  of  Railroad 
Construction,"  etc. 


Authorities  Consulted— Continued 


EDWARD  R.  MAURER,  B.  C.  E. 

Professor  of  Mechanics,  University  of  Wisconsin 

Joint  Author  of  "Principles  of  Reinforced  Concrete  Construction' 


HERBERT  M.  WILSON,  C.  E. 

Geographer  and  Former  Irrigation  Engineer,  United  States  Geological  Survey;  American 

Society  of  Civil  Engineers 
Author  of  "Topographic  Surveying,"  "Irrigation  Engineering,"  etc. 


MANSFIELD  MERRIMAN,  C.  E.,  Ph.  D. 

Consulting  Engineer 

Formerly  Professer  of  Civil  Engineering,  Lehigh  University 

Author  of  "The  Elements  of  Precise  Surveying  and  Geodesy,"  "A  Treatise  on  Hy- 
draulics," "Mechanics  of  Materials,"  "Retaining  Walls  and  Masonry  Dams," 
"Introduction  to  Geodetic  Surveying,"  "A  Textbook  on  Roofs  and  Bridges,"  "A 
Handbook  for  Surveyors,"  "American  Civil  Engineers'  Pocket  Book" 


DAVID  M.  STAUFFER 

American  Society  of  Civil  Engineers;  Institution  of  Civil  Engineers;  Vice-President, 

Engineering  News  Publishing  Co. 
Author  of  "Modern  Tunnel  Practice" 


CHARLES  L.  CRANDALL 

Professor  of  Railroad  Engineering  and  Geodesy  in  Cornell  University 
Author  of  "A  Textbook  on  Geodesy  and  Least  Squares" 


N.  CLIFFORD  RICKER,  M.  Arch. 

Professor  of  Architecture,  University  of  Illinois;  Fellow  of  the  American  Institute  of 

Architects  and  of  the  Western  Association  of  Architects 
Author  of  "Elementary  Graphic  Statics  and  the  Construction  of  Trussed  Roofs" 

^-  ^ 

W.  H.  SEARLES,  C.  E. 

Author  of  "Field  Engineering"  and  "Railroad  Spiral" 


HENRY  T.  BOVEY 

Late  Rector  of  Imperial  College  of  Science  and  Technology,  London,  England 
Author  of  "Treatise  on  Hydraulics" 


WILLIAM  H.  BIRKMIRE,  C.  E. 

Author  of  "Planning  and  Construction  of  High  Office  Buildings,"  "Architectural  Iron 
and  Steel,  and  Its  Application  in  the  Construction  of  Buildings,"  "Compound 
Riveted  Girders,"  "Skeleton  Structures,"  etc. 


Authorities  Consulted— Continued 


IRA  0.  BAKER,  C.  E. 

Professor  of  Civil  Engineering,  University  of  Illinois 

Author  of  "A  Treatise  on  Masonry  Construction,"  "Engineers'  Surveying  Instruments, 
Their  Construction,  Adjustment,  and  Use,"  "Roads  and  Pavements" 


JOHN  CLAYTON  TRACY,  C.  E. 

Assistant    Professor    of    Structural    Engineering,    Sheffield    Scientific    School,    Yale 

University 
Author  of  "Plane  Surveying:  A  Textbook  and  Pocket  Manual" 


FREDERICK  W.  TAYLOR,  M.  E. 

Joint  Author  of  "A  Treatise  on  Concrete,  Plain  and  Reinforced' 


J.  B.  JOHNSON,  C.  E. 

Author  of  "Materials  of  Construction;"  Joint  Author  of  "Design  of  Modern  Frame 
Structures" 

FRANK  E.  KIDDER,  C.  E.,  Ph.  D. 

Consulting  Architect  and  Structural  Engineer;  Fellow  of  the  American  Institute  of 
Architects 

Author  of  "Architect's  and  Builder's  Pocketbook,"  "Building  Construction  and  Super- 
intendence, Part  I,  Masons'  Work;  Part  II,  Carpenters'  Work;  Part  III,  Trussed 
Roofs  and  Roof  Trusses,"  "Strength  of  Beams,  Floors,  and  Roofs" 

V» 

WILLIAM  H.  BURR,  C.  E. 

Professor  of  Civil  Engineering,  Columbia  University;  Consulting  Engineer;  American 

Society  of  Civil  Engineers;  Institution  of  Civil  Engineers 
Author  of  "Elasticity  and  Resistance  of  the  Materials  of  Engineering:"  Joint  Author  of 

"The  Design  and  Construction  of  Metallic  Bridges,"   "Suspension  Bridges,  Arch 

Ribs,  and  Cantilevers" 


WILLIAM  M.  GILLESPIE,  LL.  D. 

Formerly  Professor  of  Civil  Engineering  in  Union  University 

Author  of  "Land  Surveying  and  Direct  Leveling,"  "Higher  Surveying' 


GEORGE  W.  TILLSON,  C.  E. 

Past  President  of  the  Brooklyn  Engineers'  Club;  American  Society  of  Civil  Engineers; 

American  Society  of  Municipal  Improvements 
Author  of  "Street  Pavements  and  Street  Paving  Material" 


CHARLES  E.  FOWLER 

Consulting  Civil  Engineer;  Member,  American  Society  of  Civil  Engineers 
Author  of  "Practical  Treatise  on  Subaqueous  Foundations" 

W.  M.  PATTON 

Late  Professor  of  Engineering  at  the  Virginia  Military  Institute 
Author  of  "A  Treatise  on  Civil  Engineering" 


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For  e  w^ord 


OF  all  the  works  of  man  in  the  various  branches  of  en- 
gineering, none  are  so  wonderful,  so  majestic,  so  awe- 
inspiring  as  the  works  of  the  Civil  Engineer.  It  is  the  Civil 
Engineer  who  throws  a  great  bridge  across  the  yawning  chasm 
which  seemingly  forms  an  impassable  obstacle  to  further 
progress.  He  designs  and  builds  the  skeletons  of  steel  to  dizzy 
heights,  for  the  architect  to  cover  and  adorn.  He  burrows 
through  a  great  mountain  and  reaches  the  other  side  within  a 
fraction  of  an  inch  of  the  spot  located  by  the  original  survey. 
He  scales  mountain  peaks,  or  traverses  dry  river  beds,  survey- 
ing and  plotting  hitherto  unknown,  or  at  least  unsurveyed, 
regions.  He  builds  our  Panama  Canals,  our  Arrow  Rock  and 
Roosevelt  Dams,  our  water-works,  filtration  plants,  and  prac- 
tically all  of  our  great  public  works. 

C  The  importance  of  all  of  .these  immense  engineering 
projects  and  the  need  for  a  clear,  non-technical  presentation  of 
the  theoretical  and  practical  developments  of  the  broad  field 
of  Civil  Engineering  has  led  the  publishers  to  compile  this 
great  reference  work.  It  has  been  their  aim  to  fulfill  the  de- 
mands of  the  trained  engineer  for  authoritative  material  which 
will  solve  the  problems  in  his  own  and  allied  lines  in  Civil 
Engineering,  as  well  as  to  satisfy  the  desires  of  the  self-taught 
practical  man  who  attempts  to  keep  up  with  modern  engineer- 
ing developments. 


^  Books  on  the  several  divisions  of  Civil  Engineering  are 
many  and  valuable,  but  their  information  is  too  voluminous  to 
be  of  the  greatest  value  for  ready  reference.  The  Cyclopedia  of 
Civil  Engineering  offers  more  condensed  and  less  technical 
treatments  of  these  same  subjects  from  which  all  unnecessary 
duplication  has  been  eliminated;  when  compiled  into  nine 
handy  volumes,  with  comprehensive  indexes  to  facilitate  the 
looking  up  of  various  topics,  they  represent  a  library  admirably 
adapted  to  the  requirements  of  either  the  technical  or  the 
practical  reader. 

^  The  Cyclopedia  of  Civil  Engineering  has  for  years  occupied 
an  enviable  place  in  the  field  of  technical  literature  as  a 
standard  reference  work  and  the  publishers  have  spared  no 
expense  to  make  this  latest  edition  even  more  comprehensive' 
and  instructive. 

^  In  conclusion,  grateful  acknowledgment  is  due  to  the  staff 
of  authors  and  collaborators — engineers  of  wide  practical  ex- 
perience, and  teachers  of  well  recognized  ability  —  without 
whose  hearty  co-operation  this  work  would  have  been  im- 
possible. 


Table    of    Contents 


VOLUME  II 
Railroad  Engineering  .        .        .By  Walter  Loring  Webbt      Page    *11 

Railroad  Surveys — Conflicting  Interests — Reconnoissance — Use  of  Existing  Maps 
— Surveying  Methods — Elements  of  a  Survey — Low  Ruling  Grades — Preliminary 
Surveys  —  Cross-Section  and  Stadia  Methods  —  Composition  of  Parties  —  Re- 
surveys— Location  Surveys— Selecting  a  Route— Simple  Curves— Methods  of 
Field  Work  —  Locating  Points  by  Deflections  —  Instrumental  Work  —  Special 
Methods  of  Location— Obstacles  to  Location— Modifications  of  Location — Com- 
pound Curves— Transition  Curves— Spiral  between  Tangent  and  Circular  Curve 
—Spirals  in  Old  Track— Vertical  Curves— Construction— Earthwork— Slopes  and 
Cross-Sections — Width  of  Roadbed — Ditches — Earthwork  Surveys — Position  of 
Slope  Stakes  —  Computing  the  Volume  —  Level,  Equivalent,  and  Three-Level 
Sections — Irregular  Sections— Prismoidal  Correction— Volume  of  Earthwork  in 
Irregular  Ground— Side- Hill  Work— Borrow  Pits — Correction  for  Curvature- 
Eccentricity  of  Center  of  Gravity— Methods  of  Excavating— Blasting— Formation 
of  Embankments — Tunnel  Surveys— Surveying  Down-Shafts— Tunnel  Design— 
Cross-Sections,  Grade,  Lining — Portals — Tunnel  Construction — Trestles — Pile- 
Driving  —  Trestle  Floor-Systems  —  Guard  Rails  —  Fire  Protection  —  Culverts — 
Cattle  Passes— Water  Supply— Turntables— Coaling  Stations— Engine  Houses- 
Cattle  Guards— Track  Construction— Ballast— Rails  and  Joints— Tie- Plates — 
Braces,  Spikes,  Bolts,  Nut  Locks— Laying  Ties  and  Rails — Switches  and  Turn- 
outs— Crossings— Yards  and  Terminals— Signal  Systems  (Manual,  Automatic, 
Electro- Pneumatic)  —  Semaphores  —  Interlocking  —  Track  Maintenance  —  Work 
Trains— Railroad  Finances:  Capitalization,  Stocks  and  Bonds,  Gross  Revenue, 
Fixed  Charges.  Net  Revenue,  Operating  Expenses,  Maintenance  of  Way  and 
Structures,  Maintenance  of  Equipment,  Transportation  Expenses — Economic 
Location:  General  Principles — Reliability  and  Value  of  Economic  Locations — 
Distance:  Relation  to  Rates  and  Expenses  —  Effect  on  Receipts  —  Curvature: 
Operating  Disadvantages,  Compensation  for  Curvature,  Limitations  —  Grade: 
Distinction  between  Minor  and  Ruling  Grades,  Laws  of  Accelerated  Motion, 
Virtual  Profile,  Train  Systems,  Locomotive  Ratings,  Units  of  Operation, 
Locomotive  Types,  Power  Calculations,  Effect  of  Grade  on  Tractive  Power, 
Speed  Curves  —  Pusher  Grades:  Economy,  Operation  of  Pusher  Engines,  Cost 
of  Service— Balance  of  Grades  for  Unequal  Traffic 


EARTHWORK By  A.  B.  McDaniel        Page  301 

Scrapers:  Slip— Two-Wheel— Four- Wheel— Graders:  Two- Wheel  Blade— Four- 
Wheel  Blade  —  Reclamation  —  Elevating  —  Cost  of  Operation  —  Power  Shovels: 
Fixed  and  Revolving  Platform  T^pes:  Platforms,  Power  Equipment,  Excavating 
Equipment,  Operation,  Cost  —  Electrically  Operated  Shovels  —  Efficiency  and 
Economy — Dry-Land  Excavators:  Stationary  Scrapers — Revolving  Excavators — 
Operation  Cost  —  Templet,  Wheel,  and  Tower  Excavators  —  Walking  Scoop 
Dredgea-r Walking  Drag- Line  Excavators 


Review  Questions Page  439 

Index Page  451 


*For  page  numbers,  see  foot  of  pages, 

t  For  professional  standing  of  author,  see  list  of  Authors  and  Collaborators  at 
front  of  volume. 


^  Xi 
CO    13 

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RAILROAD  ENGINEERING. 

PART  I. 


RAILROAD  SURVEYS. 

1,  General  Principles.  The  engineer  should  have  first,  a 
thorough  appreciation  of  the  objects  to  be  accomplished  by  the 
sxirveys.  He  should  realize  that,  except  in  the  rare  cases  where  it 
is  difficult  to  find  arnj  practicable  line,  very  little  engineering 
training  or  ability  is  required  to  lay  out  aline  over  which  it  would 
be  physically  possible  to  run  trains.  A  line  as  laid  out  may  violate 
all  rules  of  location,  may  be  expensive  to  operate  and  have  disad- 
vantages which  will  discourage  traffic,  and  yet  trains  can  be  run 
over  it.  From  the  infinite  number  of  possible  locations,  the  en- 
gineer must  select  the  location  which  best  satisfies  the  various  con- 
flicting interests.  His  value  as  an  engineer  depends  on  his  ability 
to  interpret  the  natural  conditions  and  design  the  line  accordingly. 
This  ability  is  only  obtained  by  a  thorough  knowledge  of  the  whole 
subject  of  railroad  engineering,  supplemented  by  practical  expe- 
rience. It  is  therefore  true  that  many  of  the  following  statements 
will  not  be  thoroughly  appreciated  until  the  student  has  covered 
the  whole  subject  and  then  reviews  it. 

2.  Conflicting  Interests.  There  are  several  classes  of  inter- 
ests, which  are  generally  more  or  less  conflicting,  which  affect  the 
location  of  every  line* 

(a)  The  initial  cost  should  he  a  miniimun,  but  the  cheap- 
est road  generally  has  sharp  curvature,  steep  grades  and  incon- 
venient location. 

(h)  The  oj?erating  expenses  per  train  mile  should  he  a 
nilthlmun},  which  is  generally  equivalent  to  saying  that  the  curva- 
ture should  be  light  and  the  grades  low,  but  this  is  usually  unob- 
tainable except  at  great  cost. 

\^6')  The  location  should  he  convenient  to  sources  of  traffic 
so  that  the  maximum  traffic  will  be  obtained,  but  this  is  generally 
very  costly. 


2  RAILROAD  ENGINEERING 

A  little  study  will  show  the  frequent  conflict  of  tlie  above 
conditions.  When  a  proposed  location  evidently  combines  the 
above  interests  advantageously,  instead  of  bringing  them  into  con- 
flict, then  there  is  no  doubt  as  to  the  proper  location,  unless  it 
affects  unduly  the  adjacent  location.  The  best  engineering  ability 
is  a  cheap  investment  when  deciding  on  a  location  which  requires 
a  delicate  balancing  of  the  claims  of  several  possible  routes,  each 
with  its  own  combination  of  greater  or  less  initial  cost,  greater  or 
less  operating  expenses,  and  greater  or  less  effect  on  the  probable 
revenue  of  the  road. 

RECONNOISSANCE  SURVEYS. 

3.  Essential  Problem.  From  the  above  considerations  it  may 
readily  be  seen  that  the  first  survey  to  be  made  (called  the  recon- 
noissance  survey)  consists  essentially  of  a  broad  examination  ot 
the  country  through  which  the  road  is  expected  to  pass.  Business 
considerations  usually  predetermine  that  the  road  is  to  connect 
certain  termini  and  also  pass  through  certain  intermediate  impor- 
tant towns  or  cities,  but  the  problem  consists  in  finding  the  best 
route  between  the  predetermined  points.  When  two  consecutive 
predetermined  points  lie  in  the  same  valley  or  on  the  same  bank  of 
a  river  too  large  to  be  easily  bridged,  the  location  is  self-evident. 
If  the  river  is  smaller,  easily  bridged,  has  sharp  bends,  with 
variable  banks  and  important  towns  on  either  bank,  it  will  usually 
require  a  close  examination  of  each  bank  to  determine  where  to 
cross  if  at  all.  When  the  two  points  are  many  miles  apart,  lie  in 
different  valleys,  and  are  therefore  separated  by  one  or  more  sum- 
mits, the  selection  of  the  best  route  becomes  more  and  more  com- 
plicated as  the  number  of  possible  routes  becomes  greater.  It  is 
generally  true,  although  not  invariably,  that  a  cross-country  route 
which  includes  the  lowest  summits  and  the  highest  loio^'point^ 
(such  as  river  crossings)  will  give  the  best  grades.  Since  the 
"  ruling  grade  "  is  the  most  important  physical  consideration  for 
the  engineer,  as  will  be  developed  later,  the  chief  work  of  the 
reconnoissance  survey  (apart  from  considerations  of  probable 
traffic)  is  the  determination  of  the  elevations  of  summits  and 
sags  and  the  distance  between  them,  together  with  the  constructive 
character  of  the  country. 


RAILROAD  ENGINEERING  8 

4.  Utilization  of  Existing  Maps.  The  U.  S.  Geological 
Survey  lias  already  published  contour  iiiaj)s  of  a  large  part  of  the 
country  which  enable  an  engineer  to  select  a  line  with  even 
greater  ease  and  certainty  than  he  can  from  a  reconnoissance  map 
made  for  the  purpose  (as  usually  made),  since  the  U.  S.  G.  S.  maps 
show  the  whole  country  and  enable  the  engineer  to  rapidly  com-- 
pare  a  dozen  suggested  routes  instead  of  confining  his  attention  to 
the  (usually)  limited  area  of  the  special  map.  The  errors  of  the 
U.  S.  G.  S.  maps  will  seldom  if  ever  be  sufficient  to  vitiate  the 
accuracy  of  the  preliminary  route  laid  out  from  them.  Usually  a 
brief  study  of  the  map  will  demonstrate  that  one  (or  perhaps  two 
or  three)  general  route  has  advantages  so  pronounced  over  all 
other  possible  routes  that  the  choice  is  immediately  made  or  is  at 
least  reduced  to  the  comparison  of  two  or  three  lines  which  are  so 
nearly  equal  that  closer  and  more  detailed  surveys  are  necessary 
to  decide  between  them.  County  atlases  are  usually  sufiiciently 
accurate  for  reconnoissance  purposes  to  the  extent  of  giving  the 
relative  horizontal  positions  of  governing  points  of  the  survey. 
Elevations  may  be  determined  (as  described  later)  and  plotted  on 
these  maps. 

5.  Surveying  Methods.  When  reliable  contour  maps  are 
unavailable,  some  of  the  following  methods  may  be  used  to  fill  out 
existing  maps  or  to  make  a  complete  reconnoissance  survey.  The 
essential  point  is  the  rapid  determination  of  those  details  from 
which  one  route  is  shown  to  be  superior  to  another.  Nothing 
useless  should  be  surveyed  and  no  time  should  be  wasted  on  an 
unnecessary  degree  of  accuracy.  The  physical  characteristics  of 
two  routes  have  usually  such  differences  that  they  are  apparent 
even  with  rapid  and  approximate  methods  of  surveying.  If  two 
routes  are  so  nearly  equal  that  a  decisive  choice  cannot  be  made 
from  the  results  of  reconnoissance  surveys,  it  shows  that  a  more 
accurate  survey  should  be  made  of  both  routes. 

6.  Elements.  The  three  elements  of  the  survey  of  any  line 
are  {a)  the  length,  (J)  the  direction,  and  {c)  the  slope  or  the  relative 
elevation  of  the  two  ends.  Distance.  The  length  is  sometimes 
determined  with  sufficient  accuracy  by  pacing,  the  steps  being 
counted  with  a  pedometer.  In  an  open  prairie  country,  where  a 
buggy  may  be  run,  an  odometer  attached  to  a  wheel  will  count  the 


4  RAILROAD  ENGINEERING 

revolutions.  An  odometer  on  a  wheel,  attached  to  a  frame  and 
trundled  like  a  wheelbarrow,  has  been  used  for  the  same  purpose. 
A  large  telescope,  mounted  with  a  universal  joint  on  a  very  light 
tripod,  and  fitted  with  stadia  wires  so  adjusted  that  distances  of 
2,000  or  even  2,500  feet  can  be  read  to  the  nearest  10  feet  on  a 
10-foot  rod,  will  give  the  distances  between  widely  separated  sta- 
tions with  sufficient  accuracy  and  extreme  rapidity.  Direction 
may  be  obtained  with  sufiicient  accuracy  with  a  compass — even  of 
the  pocket  type.  Leveling,  Spirit  leveling  is  too  slow  and  ex- 
pensive  for  the  rapid  surveying  here  required.  If  stadia  methods 
are  used  with  an  instrument  provided  for  reading  vertical  angles, 
the  inclination  of  all  lines  may  be  observed  and  the  elevations  of 
all  stations  computed.  A  still  more  rapid  method  of  observing 
differences  of  elevation  with  sufiicient  accuracy  for  the  purpose  is 
found  in  the  use  of  an  aneroid  barometer,  supplemented  by  another 
aneroid  or  preferably  by  a  mercurial  barometer.  The  mercurial, 
or  the  office  aneroid,  is  kept  at  some  ofticp  whose  elevation  is  known 
and  observations  are  regularly  taken  (say  every  half  hour)  during 
the  period  when  observations  are  being  taken  in  the  field  with  the 
field  aneroid.  The  field  aneroid  is  taken  to  each  place,  within  a 
range  of  several  miles,  where  elevations  are  desired.  At  each  point 
there  should  be  noted  (see  the  form  of  notes  below)  the  time,  the 
described  location,  the  aneroid  reading  and  the  temperature.  If 
possible,  duplicate  readings  should  be  taken  on  the  trip  to  and  from 
the  office  on  all  important  points.  The  elevations  of  succeeding 
office  locations  made,  may  be  determined  with  the  field  aneroid  if 
necessary,  but  of  course  extra  care  should  be  taken  with  such  work. 
Aneroids  are  usually  "compensated  for  temperature,"  i.e.^  so 
adjusted  that  they  will  give  a  true  reading  regardless  of  temperature. 
If  an  aneroid  has  not  been  so  adjusted,  it  should  be  carefully  com- 
pared with  a  standard  mercurial  barometer  under  widely  varying 
conditions  of  temperature  and  a  tabular  form  should  be  made  out 
for  that  aneroid  showing  the  correction  to  be  applied  at  any  given 
temperature.  On  account  of  the  expansion  of  mercury  with  tem- 
perature, and  also  the  expansion  (at  a  different  rate)  of  the  tube 
and  cistern,  all  readings  of  the  mercurial  barometer  must  be 
"reduced  to  32°  F.,"  i.e.^  reduced  to  the  reading  it  would  have,  if 
the  temperature  of  the  instrument  were  32°  F.     This  is  readily  ac- 


BAILROAD  ENGINEERING  5 

complished  by  means  of  Table  XI.*  At  the  office,  each  half -hourly 
observation  should  include  the  time,  the  ijeading  of  the  scale  show- 
ing the  height  of  the  mercury,  the  reading  of  the  "attached  ther- 
mometer" (the  thermometer  attaclied  to  the  mercurial)  and  also 
the  temperature  of  the  external  air.  When  the  mercurialis  in- 
doors these  two  temperatures  may  differ  somewhat.  When  reduc- 
ing the  observations  interpolation  should  be  made  if  necessary 
between  the  reduced  office  observations  to  determine  the  probable 
reading  of  the  mercurial  at  the  time  of  any  given  field  observation. 
Determine  from  Table  XII*  the  heights  corresponding  to  the  field 
reading  and  reduced  office  reading  for  each  pair  of  observations. 
Their  difference  is  the  approximate  difference  of  elevation  of  the 
office  and  of  the  place  of  the  field  observation.  If  necessary  this 
may  be  corrected  by  an  amount  equal  to  the  approximate  differ- 
ence of  elevation  :imes  a  coefficient  derived  from  Table XIII.*  This 
coefficient  is  found  opposite  the  number  which  gives  the  sum  of  the 
temperatures  in  the  field  and  outside  the  office.  The  correction  is 
frequently  too  small  to  be  noticed.  An  approximate  calculation 
will  often  show  this,  or  will  give  a  solution  to  the  nearest  foot, 
which  is  amply  accurate.  An  aneroid,  no  matter  how  perfect,  will 
seldom  agree  exactly  with  a  mercurial  barometer,  and  even  if  ad- 
justed to  the  same  reading  will  soon  indicate  some  discrepancy. 
It  is  therefore  better  to  leave  the  adjustment  undisturbed  and 
apply  corrections.  The  aneroid  should  therefore  be  compared  with 
the  mercurial  before  leaving  headquarters  for  a  day's  work,  and 
the  readinors  of  both  and  their  diiference  should  be  recorded. 
Immediately  after  returning  from  the  day's  work  the  aneroid  should 
again  be  compared.  The  absolute  reading  of  the  mercurial  will 
probably  be  higher  or  lower,  but  the  difference  should  be  nearly 
the  same,  although  it  is  found  that  an  aneroid  will  lag  somewhat 
behind  its  true  reading,  especially  if  it  has  been  subjected  to  an 
extreme  variation  of  pressure.  All  the  field  readings  of  the  an- 
eroid should  therefore  be  corrected  by  the  mean  of  the  initial  and 
final  differences.  The  method  and  the  above  explanation  may  be 
illustrated  by  the  following  numerical  examples: 

7.  '  Examples.     1.     Given   a   reading   of   28.692  on  a  mer- 

*See  Webb's  "Trigonometric  Tables,"  pubUshed  by  American  School  of  Correspond- 
ence, Chicago,  111.    Price,  50c, 


6 


RAILROAD  ENGINEERING 


curial  barometer,  what  is  its  reading  when  reduced  to  32°  F.,  the 
reading  of  the  attached  thernionieter  being  68. 5"^  F.?  In  Table 
XI*  under  28.5  and  opposite  68",  we  find  -  .101.  Under  29.0  and 
for  68°  we  find  -  .103.  For  28.692  and  68°  it  evidently  should  be 
-  .102  (to  the  nearest  thousandth).  Similarly  for  28.692  and  69° 
we  may  derive  -  .105.  For  28.692  and  68.5°  it  w^ould  be  the  mean 
or  -  .1035,  which  we  will  call  -  .103  since  it  is  useless  to  compute 
the  correction  closer  than  the  nearest  thousandth.  Then  since  the 
correction  is  -  .103,  the  corrected  reading  should  be  28.589.  With 
a  little  practice  the  interpolations,  when  necessary,  may  be  made 
in  far  less  time  than  it  takes  to  describe  it. 
2.     Verify  the  following  reductions: 


Bar.  reading. 

Temp. 

Reduced  reading. 

26.426 
27.892 
28.475 
30.847 

58°  F. 
78.5 
85. 
48.5 

26.356 
27.767 
28.a30 
30.792 

3.  Reduce  the  following  readings:  27.294,  47°;  29.462,  87°; 
26.230,  78.5°;  25.241,  62°;  26.481,  75°;  29.625,  89.5°;  30.942, 
88.5°;  29.784,  46.5°;  28.386,  48°;  27.942,  74.5°. 

4.  Compute  the  barometric  elevation  corresponding  to  a 
reading  of  28.589.  From  Table  XII*  the  reading  for  28.5  is  1397 
and  the  difference  for  .01  is  -9.5;  therefore,  for  .089  the  correction 
will  be  -9.5  X  8.9  =  -  84.55,  or  in  whole  numbers  -  85.  Then 
1397  -  85  ==  1312,  the  corrected  reading. 

5.  Verify  the  following  elevations  from  the  reduced  read- 
ings: 26.356,  27.767,  28.330,  and  30.792;  i.e.,  3528,  2107,  1560, 
and  -  710. 

6.  Compute  the  barometric  elevations  corresponding  to  the 
reduced  readings  found  by  solving  Example  3. 

7.  With  an  approximate  difference  of  elevation  of  -  136  feet 
and  field  and  ofiice  temperatures  of  62°  and  67°,  what  is  the  true 
difference  of  elevation?  62  +  67  =  129.  For  129°  the  coefii- 
cient  is  (by  interpolation)  +  .0357.  136  X  (+  .0357)=  +4.8552. 
For  this  slight  difference  of  elevation,  the  coefficient  is  far  more 
accurate  than  necessary,  and  of  course  the  correction  is  called  +  5. 

♦See  Webb's  "Trigonometric  Tables,"  published  by  American  School  of  Correspond- 


RAILROAD  ENGINEERING 


The  difference  of  elevation  should  be  increased  by  5,  but  the  dif- 
ference is  essentially  negative.  Therefore  we  have  as  the  correc- 
tion -(+  5).  The  true  difference  of  elevation  is  - 136  -  (-|-  5)  = 
-141. 

8.  The  following  example  shows  not  only  the  method  of 
recording  the  observations  but  also  the  complete  solution  of  a 
problem. 


Time. 

Mercurial 

Attached 

Reduction  to 

Corrected 

External 

barometer. 

thermometer. 

320  F. 

reading. 

thermometer. 

7:00  A.  M. 

28.692 

62° 

-.087 

28.605 

60°  F. 

:30 

.724 

64 

-.092 

.632 

62 

8:00 

.756 

66.5 

-.099 

.657 

64 

:30 

.782 

68 

-.102 

.680 

65 

9:00 

.824 

69 

-.105 

.719 

66 

The  observations  taken  in  the  field  at  this  time  were  as  given 
in  the  first  four  columns  of  the  following  tabular  form.  The 
other  columns  are  computed  later  in  the  office. 

(Left-hand  page  of  notes.) 


Time. 

Place. 

Aneroid. 

Therm. 

Corrected 
aneroid. 

Corrected 
mercurial. 

7:00  A.  M. 

Office. 

28.743 
.769 
.860 

.522 

62° 

63 

65 

66 

28.605 

7:20 
8:10 

8:50 

R.  R.  Junction. 

Blue  River 

Saddle  in 
Beanpole  ridge 

28.631 
.722 

.384 

.623 
.665 

.706 

(Right-hand  page  of  notes.) 


Ext.  temp, 
office. 

Approx.  field 
reading. 

Approx.  office 
reading. 

Difference. 

Correction 
for  temp. 

Difference  of 
elevation. 

62° 

64 

66 

i27'3 
1186 
1508 

1280 
1240 
1201 

-54 
+  307 

0 

-(+2) 
+  12 

-56 
+  319 

8.  Low  Ruling  Grades.  It  will  be  developed  later  that  a 
low  ruling  grade  is  of  prime  importance.  The  approximate  value 
of  the  ruling  grade  is  determined  from  the  reconnoissance  survey. 
If  the  country  is  mountainous,  it  may  be  necessary  to  "develop" 
the  line   in   order    to    reduce    the   grade.     *•  Development"    here 


RAILROAD  ENGINEERING 


RAILROAD  EXGTNEERING  0 

ineans  a  deliberate  increase  in  the  length  of  the  line  between  two 
predetermined  points  so  that  the  rate  of  grade  shall  be  as  low  as 
desired.  The  Georgetowni  spiral,  shown  in  Fig.  1,  is  perhaps  the 
most  famous  example  in  this  country  of  this  general  method.  A 
study  of  the  course  of  the  track  will  illustrate  several  methods  of 
taking  advantage  of  the  topography  and  attaining  a  considerable 
elevation  although  the  grade  is  kept  low. 

PRELIMINARY  SURVEYS. 

9.  General  Object.  The  reconnoissance  survey  has  shown 
tliat  the  best  location  for  the  road  will  lie  somewhere  throuo^h  a 
certain  belt  of  country.  In  some  places  this  belt  may  be  very 
narrow,  i.e.,  certain  topographical  features  will  determine  that  the 
road  must  pass  through  a  strip  but  little  if  any  wider  than  the 
roadbed  requirements.  In  other  places  the  choice  of  possible  loca- 
tion is  so  widened  that  it  is  necessary  to  survey  everything  within 
reach  of  the  backbone  line  of  the  survey.  The  willingness  or  finan- 
cial ability  of  the  company  to  ignore  minor  topographical  con- 
siderations and  incur  heavy  expense  in  order  to  obtain  economic 
advantages,  may  also  widen  the  area  of  possible  location.  As  a 
general  statement,  the  width  of  the  belt  surveyed  should  so  vary 
as  to  include  all  practicable  locations  along  that  general  route. 

10.  Cross  Section  Method.  A  broken  line  is  run  which 
shall  lie  as  near  the  expected  location  line  as  possible.  The  bear- 
ing and  length  of  each  segment  of  the  broken  line  is  determined 
and  also  all  essential  topographical  features  on  either  side.  Bear- 
ings are  sometimes  taken  only  with  a  compass,  which  has  the 
advantage  of  great  rapidity  but  lessened  accuracy.  For  more  ac- 
curate work,  true  azimuth  is  carried  along  by  means  of  back  sights 
at  previous  stations.  The  azimuths  between  stations  should  be' 
checked  by  means  of  needle  readings.  It  is  advisable  to  determine 
exact  azimuth  at  the  beginning  of  a  survey  and  at  intervals  of  a 
few  miles.  This  may  be  done  by  observations  on  Polaris  (see 
Plane  Surveying,  Part  II,  Pages  '95  to  97),  or  still  better,  by  solar 
observations  w4iich  may  be  taken  w^ith  great  accuracy  at  any  time 
of  day.  Set  stakes  at  each  even  100  feet.  In  general  the  instru- 
ment stations  will  not  occur  at  the  even  100-foot  distances,  but  the 
odd  distance  should  always  be  carried  on  to  the  next  course.     The 


10  RAILROAD  ENOINEERINO 

stakes  should  be  about  fifteen  inches  long  and  about  one-and-one 
quarter  inches  square.  Stakes  with  a  cross-section  of  one  inch  by 
one-and-one-half  inches  are  preferred  by  some.  The  stakes  indi- 
cating the  100-foot  stations  should  be  driven  to  within  five  inches 
of  the  ground.  Stakes  indicating  the  locations  of  the  transit  (called 
hubs)  should  be  driven  flush  with  the  ground.  A  "  witness  stake" 
should  then  be  driven  three  feet  to  the  right  and  on  this  stake 
should  be  marked  the  station  number  and  the  "plus  distance  "; 
e.g.^  the  stake  might  show  137  +  46,  which  would  indicate  that  the 
stake  was  46  feet  beyond  Sta.  137,  and  13,746  feet  from  the  start- 
ing point.  Station  stakes  should  be  marked  with  the  station 
number  on  the  rear  side  of  the  stake.  Immediately  following  the 
transit  party,  the  level  party  should  obtain  the  elevations  above  the 
datum  plane  of  all  stations  and  substations,  ridges,  sags,  river  banks 
and  any  point  where  the  profile  changes  abruptly. 

11.  Cross  Sectioning.  Use  a  Locke  level,  resting  on  a  five- 
foot  stick,  a  50-foot  tape  and  a  ten -foot  rod  graduated  to  feet  and 
tenths.  The  cross-section  party  takes  cross  sections  (usually)  at 
every  100-foot  stake,  the  cross  section  being  made  perpendicular 
to  the  backbone  line  of  the  survey  at  that  place,  as  is  indicated  by 
the  dotted  lines  in  Fig.  2.  It  is  desired  to  plot  on  the  map  con- 
tours at  each  five-foot  interval  above  the  datum  plane.  Let  Fig. 
3  represent  a  typical  cross  section.  Set  the  level  (on  its  five- foot 
stick)  at  the  stake  S.  The  elevation  of  this  stake  given  by  the 
level  party  is  (say)  169.4.  The  level  therefore  has  an  elevation  of 
l'''4.4.  If  the  level  rod  is  moved  up  hill  until  it  is  found  (by 
trial)  that  4.4  mark  is  on  a  level  with  the  telescope,  then  the  base 
of  the  rod  must  have  a  level  of  170  and  must  be  on  the  170-foot 
contour.  Measure  the  distance  horizontally  from  stake  to  rod 
and  record  as  shown  in  Fig.  4.  Leaving  the  level  rod  at  that  point, 
carry  the  stick  and  level  up  the  hill  until  a  level  line  strikes  the 
top  of  the  rod.  The  base  of  the  stick  is  evidently  on  the  175-foot 
contour.  Measure  and  record  the  distance  as  before.  Carry  the 
level  rod  to  that  point  and  in  a  similar  manner  determine  the  180 
foot  contour  if  desired.  The  165-foot  contour  is  evidently  9.4  feet 
below  the  telescope  when  on  the  5 -foot  stick  at  the  center  stake. 
The  distance  from  the  center  to  the  165-foot  contour  can  thus  be 
found.     Lower  contours  can  be  similarly  obtained.     The  results 


RAILROAD  ENGINEERING 


11 


should  be  plotted  in  a  note-book  ruled  in  quarter- inch  squares, 
each  side  of  a  square  representing  25  feet.  The  work  will  then  be 
plotted  on  the  scale  of  100  feet  per  inch.  If  the  successive  stations 
are  plotted  iip  the  page,  the  drawing  will  correspond  with  the 
points  when  looking  ahead  along  the  line.  After  plotting  each 
section,  the  corresponding  contours  should  be  connected  to  form  a 
sketch  like  Fig.  4.  The  crossing  of  the  main  line  by  a  contour 
may  be  similarly  determined.  Fig.  4  is  simply  an  enlarged  detail 
of  a  sketch  like  Fig.  2.     Although  the  Locke  level  is  incapable  of 


Fig.  2. 


accurate  leveling  work,  any  error  that  may  be  made  by  the  above 
method  is  confined  to  the  station  where  it  occurs  and  is  not  carried 
on  and  made  cumulative.  With  reasonable  care  such  inaccuracies 
can  be  kept  within  desired  limits,  while  the  rapidity  is  far  greater 
than  a  more  accurate  method. 

12.  Stadia  Method.  This  consists  simply  of  a  stadia  survey 
of  a  long  and  narrow  belt  of  country  by  the  same  general  methods 
as  those  employed  in  ordinary  stadia- topographical  surveys.  One 
advantage  of  this  method  is  that  the  levels  can  be  carried  along 
very  successfully  as  a  part  of  the  stadia  work,  if  particular  care  is 
taken  to  always  obtain  practical  agreement  in  the  vertical  angles 


12 


RAILROAD  ENGINEERING 


for  the  foresight  and  backsight  between  conse.mtive  stations.  This 
will  generally  permit  more  rapid  work,  as  the  progress  of  the 
whole  party  is   sometimes  limited   by   the  progress  of  the  level 

party.     The  added  cost 

.__^Q^ j._.  of  tlie  level  party  is  also 

saved.  It  is  here  as- 
sumed that  the  details 
of  stadia  work  have  al- 
ready been  studied  and 
therefore  no  further  dis- 
cussion will  be  given  of 
this  very  simple  appli- 
cation of  the  general 
previous  method,  the  primary  object  of  the 
survey  is  the  preparation  of  a  map  sliowing  the  contours  and 
required  topographical  features  over  tlie  desired  area. 


Fig.  3 
method.     As  in   tlie 


Fig.  4, 

13.  Party  Required.  It  has  been  forcibly  said  that  the  only 
duty  of  the  chief- of -jMvty  is  to  ^'keep  his  eyes  open".  The 
selection  of  the  best  route  for  a  road  fo  de|)ends  on  a  close  study 
of  the  country  that  if  the  chief-of-party  is  required  to  do  the  work 


RAILROAD  ENGINEERING  13 

of  traDsitman,  as  is  sometimes  the  case,  the  work  of  either  position 
is  apt  to  suffer.  The  work  of  the  transitmaii  is  so  exacting  that 
he  should  not  be  required  to  spend  any  time  in  studying  out  a 
route.  Beside  these  two,  there  should  be  two  flagmen,  two  chain - 
men,  one  stakeman  and  two  or  more  axemen — depending  on  the 
wooded  character  of  the  country.  On  stadia  surveys  the  flagmen 
and  chainmen  may  be  replaced  by  two  or  more  rodmen;  it  is  also 
economical  to  have  a  recorder,  as  it  facilitates  the  progress  of  the 
whole  party.  The  cross-section  party  should  consist  of  a  level- 
man,  recorder,  and  two  tapemen.  This  party  can  be  cut  down  to 
three,  or  in  an  emergency  two,  but  it  is  uneconomical  in  the  long 
run.  The  level  party  will  consist  of  a  leveler  and  rodman.  If 
the  party  is  camping  out,  a  cook  and  one  or  more  teamsters  will 
usually  be  required  to  handle  the  camp  equipage,  as  it  is  unwise 
to  require  the  surveyors  to  spend  their  time  in  such  work. 

14.  Re-surveys.  Much  of  the  defective  location  of  raH- 
roads  is  due  to  (1)*  deciding  hastily  on  a  general  route,  (2)  then 
surveying  a  line  through  the  belt  with  great  detail  and  accuracy, 
(3)  then  locating  the  line  substantially  as  first  surveyed,  because 
the  line  is  fairly  good  (or  at  least  not  very  bad),  and  also  because 
of  an  unwillingness  to  throw  away  the  detailed  work  of  a  large 
party  for  several  weeks.  Frequently  a  great  amount  of  unneces- 
sary and  wholly  useless  detail  is  surveyed  and  plotted  during  the 
reconnoissance  and  preliminary  surveys.  These  surveys  should 
only  include  those  salient  facts  which  instantly  stamp  a  route  as 
being  inferior  or  superior  to  another.  Usually  the  general  loca- 
tion of  a  large  part  of  a  route  is  self  evident  or  may  be  deter- 
mined after  a  brief  examination.  But  there  are  generally  places 
along  the  line  where  for  a  few  miles  a  hasty  examination  of  two 
or  three  lines  is  not  only  justifiable  but  is  the  only  proper  course. 
Two  or  more  of  these  short  loops  may  show  advantages  so  evenly 
divided  that  a  more  elaborate  survey  is  necessary  to  decide  betw^een 
them.  Even  after  the  location  survey  has  been  made,  or  even 
after  construction  has  begun,  changes  are  often  proper,  but  if  the 
preliminary  surveying  has  been  well  done  only  minor  changes 
should  be  needed.  A  few  hundred  dollars  spent  on  extra  survey- 
ing is  a  wise  investment  considering  the  great  probability  of  an 
immediate  saving  of  as  many  thousands  in  construction  or  of  an 


14  RAILROAD  ENGINEERING 

operating  advantage  whose  annual  value  might  be  as  great  as  the 
cost  of  the  extra  surveying. 

LOCATION   SURVEYS. 

15.  Selecting  a  Route.  *Much  of  the  raih-oad  location  of 
the  country  has  been  done  by  picking  out  the  line  on  the  ground, 
even  making  it  follow  in  places  the  backbone  line  of  the  prelim- 
inary survey,  running  from  one  course  to  the  next  by  means  of 
suitable  curves.  In  the  hands  of  a  good  engineer  the  method  is 
not  necessarily  very  bad,  but  it  is  much  improved  by  the  following 
modification.  Paper  location.  The  work  of  the  preliminary  sur- 
vey is  carefully  plotted  from  the  transit  notes  and  cross-section 
book  to  a  scale  of  200  feet  per  inch.  On  this  map  may  be  plotted 
one  or  more  trial  location  lines.  Each  of  these  consists  of  circular 
curves  joined  by  tangents.  The  location  line  must  pass  through 
any  predetermined  points  and  yet  join  them  by  lines  w^hich  will 
give  the  best  location,  considering  the  conflicting  interests  as 
described  in  section  1.  Within  the  limits  of  the  preliminary 
map  several  locations  are  generally  possible  and  one  great  element 
of  the  value  of  such  a  map  lies  in  the  ease  with  which  several 
routes  may  be  laid  out  and  compared.  Profiles  may  be  drawn  for 
each  line  laid  down  by  noting  the  intersection  of  the  line,  with 
each  contour.  Drawing  on  the  profile  the  required  grade  line  wull 
give  a  relative  idea  of  the  amount  of  earthwork  required.  The 
method  is  especially  valuable  when  "development"  is  necessary. 
Although  such  a  line  must  sometimes  be  laid  out  by  a  bold  and 
apparently  unsystematic  trial  of  a  route,  yet  some  approach  to  a 
systematic  solution  may  be  made  as  follows:  Assume  that  the 
maximum  ruling  grade  has  been  determined  as  1.2  per  cent,  and 
that  the  contours  have,  as  usual,  a  five-foot  interval.  It  will 
require  417  feet  of  1.2  per  cent  grade  to  rise  five  feet.  Set  a  pair 
of  dividers  so  that  they  will  step  off  spaces  of  417  feet  on  the 
map.  Starting  on  a  contour  at  the  required  beginning  of  a  grade, 
swing  the  dividers  so  that  they  will  just  reach  the  next  contour 
and  continue  to  step  off  such  spaces.  Joining  these  points,  such 
a  line  would  be  a  purely  surface  line,  would  probably  be  very 
crooked  and  otherwise  unsuitable,  but  it  probably  would  be  sug- 
gestive of  a  practicable  route*    After  locating  on  the  map  the  best 

24 


RAILROAD  ENGINEERING  15 

obtainable  line,  it  should  then  be  transferred  to  the  gronnd. 
Measure  to  scale  the  lengths  af  all  "tangents"  (the  straight  lines 
joining  the  curves),  and  the  radii  and  lengths  of  all  curves. 
Instead  of  scaling  off  the  length  of  a  curve,  it  may  be  more  accu- 
rate to  measure  with  a  protractor,  or  with  a  scale  of  chords,  the 
angle  between  the  tangents  at  each  end  of  the  curve,  and  from  the 
angle  and  the  radius  compute  the  length.  Usually  the  located 
line  will  lie  fairly  close  to  the  preliminary  line — close  enough  so 
that  tie  lines  may  readily  be  run  between  them.  These  should  be 
scaled  from  the  map.  To  prevent  the  accumulation  of  error  due 
to  inaccuracies,  the  length  (or  radii)  of  curves  or  the  length  of 
tangents  should  be  altered  if  necessary  so  as  to  make  the  location 
check  on  the  ground  with  the  positions  of  the  stakes  of  the  pre- 
liminary survey.  The  method  of  making  such  modifications  will 
be  taken  up  later. 

16.  Surveying  Methods.  Only  the  most  precise  work  with 
a  transit  can  be  tolerated.  The  compass  needle  is  only  to  be  used 
as  a  check,  but  its  use  for  this  purpose  should  be  insisted  on,  as 
it  frequently  detects  a  gross  error.  Transit  stations  should  be 
marked  by  ''hubs"  and  "witness  stakes"  (Section  10).  Reference 
stakes  should  also  be  set  at  places  as  near  as  possible  to  the  princi- 
pal stations  and  yet  outside  of  the  line  of  all  earthwork  operations, 
so  that  at  any  stage  of  the  construction  the  positions  of  the  original 
stakes  may  be  easily  recovered.  The  link  chain  as  a  measurer  has 
now  been  practically  discarded  for  the  steel  tape.  Fractions  of  a 
foot  are  measured  in  tenths  and  hundredths  rather  than  in  inches. 
The  personnel  of  the  party  will  be  almost  identical  with  that  of 
the  preliminary  survey  party  except  that  the  cross  section  party 
will  be  replaced  by  the  slope-stake  party,  whose  duties  are  similar, 
but  who  generally  use  a  level  on  a  tripod  rather  than  a  hand  level. 
The  description  of  the  duties  of  the  slope-stake  party  will  be  de- 
ferred to  a  later  chapter.  The  leveling  party  should  establish 
"bench-marks"  at  frequent  intervals  along  the  line.  A  spike 
driven  in  the  roots  of  a  large  tree  is  one  of  the  best  and  easiest  es- 
tablished of  marks  in  rural  districts.  A  mark  on  any  large 
masonry  structure,  such  as  a  bridge  abutment  or  a  building,  should 
be  obtained  when  possible.  Levels  should  be  taken  to  hundredths 
of  a  foot  on  turning  points  and  bench  marks.     Some  engineers 

25 


16  RAILROAD  ENGINEERING 

read  to  tlioiisandtlis  of  a  foot,  but  when  it  is  considered  that  one 
division  of  a  level  bubble  Tisually  corresj)onds  to  30"  of  arc,  and  that 
at  a  distance  of  150  feet  a  movement  of  30"  of  arc  will  correspond 
to  .0218  foot  on  the  rod,  an  error  of  level  amounting  to  a  very  small 
fraction  of  a  division  will  make  an  error  of  several  thousandths  or 
even  a  hundredth.  Therefore  unless  unusual  care  is  taken  in 
handling  the  level,  it  is  a  useless  refinement  to  read  the  rod  to 
thousandths.  In  reading  elevations  of  the  surface  of  the  ground, 
the  nearest  tenth  of  a  foot  is  sufficiently  accurate.  The  complete 
details  of  location  surveys  can  only  be  appreciated  after  the  subject 
of  railroad  curves  has  been  studied,  and  they  will  not  therefore  be 
further  elaborated  here. 

SIMPLE  CURVES,  * 

17.     Method  of  Measurement.     The  alignment  of  a  track  is 

the  geometrical  form  of  the  line  midway  between  the  two  rails. 

Such  a  center  line  may  be  a  straight  line,  a  simple  curve  or  a  curve 

of  double  curvature,  but  it  simplifies  matters  to  consider  always 

the  horizontal  projection  of  such  lines. 

\  Their  vertical  projections  are  considered 

^^""mC       separately  when  it  is  necessary.     Curves  are 

^^((p         m      sometimes  designated  by  their  radius  or  by 

^y(^  W\     the  degrees  and  minutes  subtended  by  a  unit 

^^■\;0  .«      chord.     Nearly  all  railroad  curves  have  such 

^"^v..,^^        Hf     long  radii  that  it  is  impracticable  to  use  the 

^"^"^^vj/      center.     Therefore  all  work  is  done  at  the 
/8 
■p.     ^  circumference  in  accordance  w^ith  geomet- 

rical principles  which  will  now  be  described. 
If  AB,  Fig.  5,  is  a  chord  of  unit  length,  then  D  is  called  \hQ degree 
of  curve  for  the  radius  R. 

AO  sin  i  D  =  i  AB  =  -4  C 


2    ^^  2 


(1) 


26 


KAIT.ROAD  ENGINEERING 


wLicli  becomes  by  inversion 


sin  -^  D 


2R 


(2) 


The  length  of  the  unit  sub-chord  varies  somewhat  with  cus. 
torn.  The  abnost  invariable  practice  in  the  United  States  is  to  use 
a  unit  chord  length  of  100  feet.  Sul)stituting  C  =  100  in  equa- 
tion 1,  and  successively  assuming  values  from  0"^  01'  up  to  12"^  0' 
varying  by  single  minutes,  and  with  larger  intervals  for  higher 
degrees  which  are  very  seldom  used,  the  radius  of  almost  any  curve 
may  be  tabulated  for  ready  and  convenient  use.  Such  a  table  is 
found  in  Table  I*,  which  also  gives  the  logarithm  of  each  radius. 
A  very  common  rule,  which  is  approximate  but  accurate  enough 
for  many  uses,  is  as  follows,  using  the  same  notation  as  before: 


_5730 


(3) 


i8.  Sub=Chords.  It  often  becomes  necessary  to  lay  oflp  a 
chord  length  which  is  less  than  100  feet  and  to  know  the  angle 
subtended  at  the  center.  Since  a  chord 
is  shorter  than  its  arc,  it  also  follows 
that  the  sum  of  the  four  equal  chords  in 
Fig.  6  is  also  shorter  than  the  total  arc 
although  they  are  evidently  longer  than 
the  100'  chord.  But  it  is  found  more 
convenient  to  say  that  the  chord  has  a 
rKjminal  length  (in  this  case)  of  25  feet. 
As  in  equation  (2)  we  may  derive 


.1  c 


(4) 


Fig.  6. 


In  which  d  is  the  angle  subtending  the  sub-chord  whose  true 
length  is  c.     By  inversion  we  have 


c  =  2  It  sin^^ 


(5) 


Calling  the  nonnmal  length  c',  we  have  the  proportion 

r':100::^Z:D 


•See  Webb's  "Trigonometric  Tables,"  published  by  American  School  of  Correspond- 
eni'G  r!hif:iy<>.  TIL     T»ric«.  .Vh-.  ^.^ 


18  RAILROAD  ENOTNEERING 

EXAMPLES   FOR    PRACTICE. 

1.  What  is  the  true  length  of  a  chord  of  a  3^  30'  curve 
whose  nominal  length  is  40  feet  ?     From  the  above  proportion, 

40 
<^=Tqq^  =  0-40  X  3.5  =  1.4°  =  1°  24'.    Substituting  in  equa- 
tion 5,  we  have 

6'  =-  2  X  1637.3  X  sin  i  (1°  24')  =  40.005. 

Note  that  the  excess  over  40  feet  is  very  small — about  one- 
sixteenth  of  an  inch.  It  is  always  small  for  low  degrees  of  curva- 
ture.    In  the  following  example  it  is  far  greater. 

2.  What  is  the  true  length  of  a  chord  of  a  12°  curve  whose 
nominal  length  is  60  feet?  Ans.  60.070.  In  this  case  it  would 
be  a  gross  error  to  neglect  to  allow  for  this  difference. 

i9.  Length  of  a  Curve.  The  length  of  a  curve  is  always 
considered  to  be  the  quotient  of  lOOA  -h  D,  in  which  A  is  the 
total  central  angle  of  the  curve  or  the  angle  between  the  terminal 
tangents.  The  mean  length  of  the  two  rails  of  a  curve  is  always 
a  little  in  excess  of  this,  but  the  excess  is  always  so  small  that  it 
has  no  practical  importance.  It  merely  adds  an  insignificant 
amount  to  the  length  of  rail  required.  Examjple.  A  4°  curve 
begins  at  Sta.  16  +  80  and  runs  to  Sta.  21  +  35.  The  nominal 
length  of  the  curve  is  455  feet.  The  actual  arc  (which  is  the 
mean  of  the  two  rail  lengths)  is 

4.55  X  4°  X  R  X  j^o  =  455.09 

which  shows  th:.t  the  excess  in  this  case  = 
.09  foot,  a  little  over  an  inch. 

20.     Elements  of  a  Curve.     The  follow- 
ing fundamental  relations  apply  to  all  curves. 
See  Fig.  7.     The  beginning  of  the  curve,  A, 
is  called  the  point  of  curve ^  PC.     The  other 
Fig.  7.  end  of  the  curve  at  B  is  called  the  point  of 

tangeney,  PT.  The  intersection  of  the  two 
tangents  is  called  the  vertex  (Y).  The  central  angle^  A,  is  the 
angle  3,t  Y  between  the  tangents,  and  it  is  equal  to  the  angle  at 
the  center,  O,  between  the  radii  drawn  to  the  PC  and  PT.     The 


RAILROAD  ENGINEERING  19 

two  equal  tangents  AY  and  BV  are  called  tangent  distances,  T. 
The  chord  AB  is  called  the  long  chords  LC.  The'distance  HG 
from  the  middle  of  the  long  chord  to  the  middle  of  the  arc  is 
called  the  middle  ordinate,  M.  The  distance  GV  from  the  middle 
of  the  arc  to  the  vertex  is  called  the  external  distance,  E.  From 
trigonometry  the  following  commonly  used  relations  are  easily 
derived. 

T  =  Rtan^A  (6) 

LC  =  2R8ingA  (7) 

M-Rvers^A  (8) 

E  =  R  exsec  -^  A  (p) 

{Note.  The  versed  sine,  abbreviated  to  vers,  and  the  exter- 
nal secant,  abbreviated  to  exsec,  are  trigonometrical  functions 
which  are  not  commonly  used  except  in  railroad  work,  and  some 
works  on  trigonometry  omit  their  discussion.  An  inspection  of 
the  figure  readily  shows  that  vers  a  =  \  -  cos  a,  and  that  exsec 
a  =  sec  a  -  1.) 

From  trigonometry  we  may  derive  the  general  equation  that 

tan  a  -f-  exsec  a  —  cot-^«.  Therefore,  by  dividing  equation  6  by 
equation  9  and  transposing  we  obtain 

Tr^Ecot  i  A  (10) 

21.  Elements  of  a  F  Curve.  The  various  elements  of  a  curve 
are  exactly  proportional  to  the  radius  and  nearly  proportional  to 
the  degree  of  curve.  Therefore  if  the  tangents,  external  distances 
and  long  chords  are  computed  from  equations  6,  7  and  9  for  var- 
ious values  of  A  from  1°  to  91°,  varying  by  10',  then  an  approxi- 
mate value  for  any  degree  of  curve  and  value  of  A  may  be  found 
by  taking  out  its  value  for  a  1°  curve  (by  interpolation  if  necessary) 
and  then  dividing  that  value  by  the  degree  of  curve.  For  low 
degrees  of  curvature  the  inaccuracy  of  this  method  is  usually  small 


20  RAILROAD  ENGINEERING 

enough  to  ]ye  neglected.  Even  for  sharper  curvature  the  values 
obtained  are  accurate  enough  for  approximate  work.  For  abso- 
lutely accurate  values  equations  6  to  9  should  be  used,  but  the 
tabular  values,  found  in  Table  II*,  may  always  be   used  as  a  check. 

22.  Numerical  Examples.  1.  What  is  the  tangent  distance 
of  a  3'  10'  curve  whose  central  angle  is  IQ^  26'  ? 

Solution,  log  R  =  8.25757 

^-  A  ==  8'  18',  log  tan  =  9.15956 

Tangent  =  261.30       log  261.80  =  2.41714 

Approximate  solution.  Interpolating  in  Table  II*  between  the 
values  for  A  =  16°  20'  and  16°  30'  we  have  the  value  827.86  as 
the  tangent  distance  for  a  1°  curve  when  the  central  angle  is  16° 
26'.  Dividing  827.36  by  3.1666  (3°  10')  we  have  261.27  as  the 
approximate  value.  The  inaccuracy  is  about  one-hundredth  of  one 
per  cent  or  in  absolute  value  about  three-eighths  of  an  inch. 

2.  Compute  the  external  distance  and  the  long  chord  for  the 
above  curve,  both  accurately  and  approximately. 

8.  Two  tangents  make  an  angle  of  18°  24'.  It  is  desired  to 
run  a  line  which  shall  pass  21.2  feet  from  the  vertex  of  the  curve. 
What  is  the  required  radius  and  the  resulting  tangent  distance? 
Indicated  solution.  The  known  quantities  are  E  and  A;  from 
equation  10  we  may  derive  T;  then  with  T  known  and  A  a  given 
quantity,  we  may  compute  R  by  an  inversion  of  equation  6. 

METHODS   OF  FIELD    WORK. 

23.  Location  of  Points  by  Deflections.  The  angle  between 
a  tangent  to  a  curve  at  any  point  and  a  secant  from  that  point  to 
any  other  point  of  the  curve,  is  measured  by  one-half  of  the  arc 
between  those  points.  It  is  also  equal  to  one-half  of  the  angle 
between  the  radii  to  those  points.  On  this  fundamental  geomet- 
rical proposition  depends  the  whole  science  of  circular-curve  loca- 
tion. As  a  corollary,  the  angle  between  two  secants  intersecting 
on  a  point  of  the  curve  is  measured  by  one-half  of  the  intercepted 
arc  or  by  one-half  of  the  angle  between  the  radii  drawn  to  the 
ends  of  the  intercepted  arc.  Applying  these  statements  to  Fig.  8 
we  have 


*See  Webb's  "Trigonometric  Tables,"  published  by  Amerieau  School  of  Correspoud- 


IIAILROAD  ENGINEERING  21 


aOh  =  ^  aCh 
hOd  =  ^  IjQd 


If  0<^  =  100  feet,  tlieii  by  definition,  the  angle  OCt^  =  D,  and 
the    angle  TOc^  =  ^  D.     Likewise   if  the  chord  ab  =^  100  feet, 

then   the  angle  aCb  =  D  and  the  angle  aOh  =  ^  D.      ^^  is  a 

subchord   subtending  the  angle  d,   and    the   angle  bOd  =  -^  d. 

Therefore  if  a  transit  is  set   up  at  the  point  O,  any  point  of  the 
curve  may  be  determined  by  measuring  the 
proper  chord  length  from  O   in  a  direction  **^'Nrf/ 

determined  by  swinging  an  angle  from  the  /  VM^ 

tangent  OT  equal  to  one-half  of  the  angle  /  /  Yo^ 

measured  at  C   between   O  and   the  desired  /  /  \\ 

point.     But  the  measurement   need    not   be  //   .^"'^ 

made  directly  from   O  if  other  points   have     c^- 

already  been  determined;  b    may  be    deter- 
mined  from  a  land  d  from    b.     Since    it  is  p.     g 
generally  impracticable  to  locate  more  than 

500  feet  of  curve  from  any  one  point,  on  account  of  natural 
obstructions  (and  sometimes  the  distance  is  very  short),  the  transit 
must  be  moved  up  to  a  new  station  already  established  on  the 
curve.  But  the  same  principles  will  apply  and  may  be  repeated 
indefinitely. 

24.  Computing  the  Deflections.  If  the  point  of  curve  is 
less  than  100  feet  from  the  last  regular  station,  the  remainder  of 
the  100  feet  must  be  laid  off  as  a  subchord.  One-hundred-foot 
chords  are  set  off  until  a  station  is  reached  which  is  within  100 
feet  of  the  end  of  the  curve  or  (numerically)  until  the  degrees  of 
central  angle  remaining  is  less  than  D.  That  remainder  is  the 
angle  for  the  final  subchord.  The  foregoing  may  be  illustrated  by 
a  numerical  case:  A  4°  curVe  is  to  begin  at  Sta.  24  +  40.  The 
central  angle  is  18°  40'.     Compute  the  deflections.     The  first  sta- 


22  RAILROAD  ENGINEERING 

tion   point   is  60  feet  beyond   the  point  of  curve.     The   subchord 

angle  is  therefore  iqqX  ^"^  =  2-4°  =  2°  24'.    The  deflection  from 

the  tangent  is  one-half  of  this  or  1°  12'.     The  deflection  for  the 

P.T.  is  one-half  of  the  total    central  angle  or  9°  20'.     Subtracting 

1°  12'  we  have  left  8°  08',  which  will  allow  for  four  deflections  of 

0°  08' 
2°  each  and  0°  08'  over,  which  will  require  a  chord  =   ■   ^^  ■   X  100 

=  6.67  feet.     The  curve  will  therefore  end  at  Sta.  29  -f-  6.67. 

18°  40' 
This  may  be  verified  or  otherwise  computed  as  follows:      — -^ — 

=  4.66667,  the  total  nominal  length  of  the  curve  in  station  lengths 
of  100  feet.  That  is,  the  length  will  be  466.67.  The  first  sub- 
chord  is  60  feet;  then  four  chords  of  100  feet;  then  a  final  subchord 
of  6.67  feet.     The  deflections   may  be  tabulated  as  follows: 


P.O.  Sta.  24  +  40 

0° 

25 

0°      +  r 

12' 

=:    r  12' 

26 

r  12'  +  2° 

=  3°  12' 

27 

3°  12'  +  2° 

=  5°  12' 

28 

5°  12'  -h  2° 

=  T  12' 

29 

7°  12'  +  2° 

=  9°  12' 

29  4-  6.67, 

,  9°  12'  +  0° 

08' 

=:  9°  20',  which  is  one- 

half  of  18°  40'  as  it  should  be. 

25.  Instrumental  Work.  The  above  numerical  case  is  com- 
paratively simple.  When  the  degree  of  curve  is  an  odd  quantity 
and  when  difiiculties  of  location  require  that  the  transit  be  set  up 
at  substations  on  the  curve,  then  the  numerical  work,  although 
worked  out  on  precisely  the  same  principle,  is  much  greater  and 
chances  for  numerical  error  are  greater.  The  following  rule  for 
instrumental  work  is  as  simple  as  any  for  the  simple  cases  and  is 
far  better  for  the  more  complicated  cases.  Compute  the  deflec- 
tions for  all  stations  and  substations  as  illustrated  above.  Set  up 
the  transit  at  the  P.O.,  and  locate  from  it  all  stations  that  may  be 
conveniently  reached.  Then  move  up  the  transit  to  a  forward 
station  and  use  the  following  rule: 

W/)e7i  the  transit  is  set  at  any  forward  station^  hael'sight  to 
ANY  previous  station  with  the  i)lates  set  at  the  deflection  angle 


RAILROAD  ENGINEERING 


23 


for  the  station  sighted  at.  Plunge  the  telescope  and  sight  at 
any  forward  station  with  the  deflection  angle  computed  for  that 
station. 

The  student  should  verify  for  himself  the  truth  of  this  rule 
by  drawing  out  a  simple  case  and  noting  the  angles  both  for  fore- 
sight and  backsight  for  any  station,  when  the  transit  is  located  at 
any  station. 

Curve  location  requires  extreme  care  on  the  part  of  field  men, 
for  a  very  slight  inaccuracy  is  apt  to  be  multiplied  until  the  error 
is  intolerable.  The  transit  should  be  very  carefully  centered  over 
hubs,  which  should  be  referred  to  points  which  will  not  be  dis- 
turbed during  construction. 

26.  Special  Methods  of  Location.  The  above  method,  using 
a  transit  and  tape,  is  the  ordinary  and  preferable  method,  but  it  is 


Fig.  9. 

sometimes  necessary  to  lay  out  a  curve  when  a  transit  is  not  at 
hand  and  there  are  sometimes  special  conditions  when  a  modifica- 
tion of  the  above  method  will  be  more  accurate.  The  engineer 
must  have  learned  the  fundamental  principles  of  curve  location  so 
thoroughly  that  he  may  decide  on  the  best  method  to  use  and  even 
to  invent  some  modification  which  may  best  suit  the  special  case 
in  hand.     A  few  of  these  special  cases  will  be  described. 

{a)  Using  tv;o  transits.  The  location  may  run  over  swampy 
ground  where  accurate  chaining  is  impracticable.  Some  point  of 
the  curve  beyond  the  swamp  may  be  located,  perhaps  by  triangu- 
lation,  by  computing  its  angle  of  deflection  and  the  length  of  the 
long  chord  (equation  7).  The  point  beyond  the  swamp  may  or  may 
not  be  the  P.  T.  Then  set  up  two  transits  simultaneously  at  the 
stations  located  on  firm  ground     The  deflection  of  each  chord  from 


24 


RAILROAD  ENOINEERINO 


pa  =  40 


hi/  ==  V  v 


in 


tlie  tangent  to  the  curve  at  tlie  instrument  point,  or  from  tlie  long 
chord,  is  a  simple  matter  of  geometry  (see  ^  23).  A  rodman  can 
locate  each  point  by  placing  himself  at  points  where  he  is  simul- 
taneously in  line  for  both  transits. 

{!>)     By  tangential  offsets.     The  solution   of  this  as  well  as 
the  following  methods  will  be  indicated  by  the  lines  in  the  figures. 

In  each  case  the  solution  is  an  appli- 
cation of  simple  geometrical  and  ti'igo- 
nometrical  principles.  The  solutions 
are  somewhat  lengrthened,  althouo-h  not 
essentially  modified,  when  the  curve 
begins  or  ends  with  a  subchord.  In 
Fig.  10,  for  example 

Oh'  =  Oa'  +  a'h'  =  40  cos  0°  36' 
+  100  cos  (1°  12'  +  1°  30') 
40  sin  0°  30'  +  100  sin  (1°  12'  +  1"  30') 

and  similarly  for  other  points. 

(c)  By  middle  ordinates.  Compute  first  the  length  of  a 
long  chord  for  tivo  stations  and  the  middle  ordinate  of  such  a  chord. 
For  subchords,  compute  the  long  chord  and  middle  ordinates  for 
an  angle  twice  that  subtended  by  the  subchord.  These  distances 
should  be  laid  off  on  the  ground  as  indicated  in  the  illustration. 
In  Fig.  11,  Oa"  is  half  the  long  chord  for  two  stations  and  a"a 
equals  the  middle  ordi- 
nate for  such  a  loner 
chord.  Lay  off  Oa  on 
the  tangent  and  measure  ' 
out  the  offset «"<7.  Meas- 
ure out  aa'  (=  a" a)  so 
that  aa'  is  perpendicular 

to  Oa\  and  produce  O*^^'  to  h.  Oa"  ==  Oa'  =  a'h.  Thus  is  h  located, 
and  (?,  cZ,  etc.,.  will  be  located  similarly.  In  Fig.  12,  an  is  half  the 
long  chord  for  twice  the  arc  Oa^  and  On  is  its  middle  ordinate. 
Compute  similarly  zy  and  z"z^  and  lay  off  on  the  ground  a  and  z. 
Compute,  as  in  the  regular  case,  aa!  and  za'  (  —  a'l>)\  h  is  then  laid 
off  as  before. 


Fig.  11. 


RAILROAD  ENGINEERING 


25 


(d)  By  offsets  from  the  long  chord.  The  geometry  involved 
is  apparent  from  an  inspection  of  Fig.  13,  in  which  is  shown  the 
general  case  of  a  cnrve  beginning  and  ending  with  a  subchord. 
All  of  the  al)ove  methods  are  mathematically  perfect  in  theory, 
hut  wlien  curves  are  thus  laid  out  without  the  aid  of  a  transit  the 
work  is  apt  to  he  inaccurate  unless  unusual  care  is  taken. 

27.  Obstacles  to  Location. 
As  in  the  previous  section,  the 
problems  are  usually  simple  ex- 
amples in  geometry  and  trigo- 
nometry, and  the  engineer  must 
select  the  solution  which  will 
give  the  best  result. 

(<?')  Vertex  inaccessible. 
Tlie  tangents  are  frequently 
lixed  by  certain  conditions,  and 
yet  the  intersection  of  the  tan- 
gents is  within  a  building  or  in  some  place  where  it  is  impossible 
to  set  up  a  transit.  In  the  case  shown  in  Fig.  14,  the  tangents 
are  given  by  the  points  «r,  J,  n  and  m.  By  measuring  the  angles 
IxfY  and  ahY  ?Li\di  the  distance  ah^  the  triangle  ahY  may  be  solved, 
and  the  distances  uY  and  ^V  computed.  The  external  angle  at  Y  is 
the  sum  of  the  angles  at  a  and  ^,  and  equals  the  total  central  angle 

A.  Having  decided  on  the 
radius,  the  tangent  distances 
are  computed  by  equation  6, 
and  then  the  differences  B^ 
and  Ka  can  be  measured  off 
and  the  P.O.  and  the  P.T.  are 
thus  obtained.     As  a  check 


Fig.  12. 


Fig.  18. 


on  the  whole  work,  the  curve,  run  in  by  the  usual  methods,  should 
end  exactly  at  B,  with  the  forward  tangent  coinciding  in  direc- 
tion with  B/?/. 

(/>)  Point  of  cwrve,  or  point  of  tangent^  inaccessible.  By 
making  a  diagram  of  the  desired  line  with  its  obstructions,  as  in 
P'ig.  15,  the  known  and  unknown  quantities  are  readily  determined, 
also  their  geometrical  relations.  For  example,  in  the  illustration 
the  position  of  V  (on  the  ground)  is  known,  as  is  also  the  distance 


26 


KAILROAD  ENGINEERING 


Fig.  14. 


AV.     Then  the  computed  position  of  A  is  known.     Assume  some 
angle  a  such  that 

K  vers  a  =  Ks  =  no  =  jjt/ 

where  s  is  in  an  accessible  position. 
Then 

?is  =  sj)  =  H  sin  a 

and  71  and  p  can  be  located  on  the 
ground.  Then,  setting  up  a  transit  at 
n,  and  turning  from  the  line  7ip  an 
angle  of  a,  the  tangent  is  determined 
and  the  remainder  of  the  curve  can  be 
run  in  as  usual.  If  the  P.T.  is  inac- 
cessible, the  curve  may  be  run  in  to 
some  point  7n,  from  which,  by  similar 

calculations  and  field  work,  the  point  x  is  obtained,  from  which 

the  tangent  can  be  continued. 

(€)     Middle  part  of  ctrrve  ohstructed.     The  curve  may  be 

run  as  usual  to  some  point  n  (Fig.  16)  which  should  preferably, 

although   not  necessarily,  be  an  even   station.     At  7i  a  chord   nvi 

may  be  run  which  will  clear  the  obstruction.     The  angle  between 

nrti  and  the  tangent  is  one-half 

the  angle  measured  by  the  arc 

nm.     From    equation  7,  the 

length  of  nm  may  be  computed 

and  then  measured  off,  thus  es- 
tablishing the  point  m,  from 

which  the  remainder  of  the 

curve  is  easily  run  in.     As  an 

illustration    of  the  elasticity  of 

this  general   method,  it    might 

under  some  conditions  be  easier 

to  run  the  dotted  curve  having 

the  same  radius  as  the  required 

curve  could  then  be  found  by  using  the  same  geometrical  principles 

used  in  §26  d. 

28.     Numerical  Examples.     Ail  problems  have  hitherto  been 

so  very  simple  that  nothing  has  been  said  about  the  details  of  solv- 


Fig.  15. 


RAILROAD  ENGINEERING  27 

ing  numerical  problems.  But  as  problems  become  more  compli- 
cated, the  greater  becomes  the  value  of  a  systematic  method  of  solu- 
tion, which  may  be  readily  reviewed,  checked  and  studied  for  the 
discovery  of  a  possible  error.  Logarithms  should  almost  invariably 
be  used  for  multiplication  and  division,  for  they  are  great  time- 
savers.  Even  if  the  student  is  unaccustomed  to  them,  it  pays  to 
become  familiar  with  them.  Such  methods  will  be  used  in  the 
following  solutions  and  the  student  is  urged  to  solve  all  such 
problems  similarly. 

1.  In  a  case  similar  to  that  sketched  in  Fig.  14,  ab  was 
measured  as  476.25;  the  angle  Nah  was  measured  as  24°  18',  and 
the  angle  Yha  34°  22'.  The  curve  is  to  be  a  3°  30'  curve.  Its 
radius   is   therefore   1637.3.     A  =  24°  18'  +  34°  22'  =  58°  40'. 

Compute  aK  and  iB.  Logarithms. 

Equation  6.  R  (3°  30')  3.21412 

tan-^A  =  tan  29°  20'  9.74969 


2 


T  =  920.04  2.96381 


3i„  340  22,                            ah  =  476.25  2.67783 

^^  ^  "^^  sin  58°  40"'                          log  sin  34°  22'  9.75165 

co-log  sin  58°  40'  0.06836 

aY  =  314.74  2.49795 
Tan  AY  =  920.04 


aA.  =  605.30 
sin  24°  18'  — 

^'^  =  ^^'  oir.  ^k-  ±(^'  cil  =  476.25  2.67783 


sin  58°  40' 


log  sin  24°  18'  9.61438 

co-log  sin  58°  40'  0.06846 

hY  =  229.45  2.36068 
Tan  BY  =  920.04 


hB  =  690.59 

2.     Example  as  in  Fig.  15.     D  =  3°  20'.     A  =  23°  40'.     It 

is  estimated  that  at  v,  180  feet  back  from  Y,  the  line  7ip  will  prob- 
ably clear  the  obstruction  at  A;  71s  is  the  difference  between  180 
and  the  computed  tangent  distance  AY;  71s  -j-  R  =  sin  a.  Then 
nv  =  py  —  R  vers  a.     Locate  7%  by  the  offset  -y??,  and  make  a 


28 


RAILROAD  ENGINEERING 


similar  oflFset  tit  //.  If  this  line  does  not  clear  tlie  ol)struction, 
another  value  of  a  (probably  greater)  should  be  assumed  and  new 
values  for  A.v  and  vii  computed.  Compute  the  numerical  values 
as  above. 

29.     Modifications  of  Location,      Only    a    few   of    the    very 
many  changes   which  are  at  times  required   will  here  be  given. 

They  are  all  solvable  by  a  few  principles 
of  geometry  and  trigonometry.  The  oc- 
casion for  many  such  changes  is  the  ad- 
justment of  the  inaccuracies  of  a  "paper 
location." 

(i)  To  move  theforumrd'  tangent  par- 
allel to  itself  a  distance  x^  the  radms 
remaining  unehanged.  See  Fig. '  17. 
Every  point  of  the  curve  is  moved  par- 
allel to  the  first  tangent  a  distance  A  A'  = 
BB'==VV'-=00'. 


Fig.  16. 


AA'=: 


B'?^ 


X 


sin  7?BB'      sin  A 


(«■) 


(^)     To  move  the  forward  tangent  parallel  to  itself  the 
point  of  curvatiire  remaining  unehanged'.     Since  the   central 
angle  (A)  is   unchanged,   the  curve  and   all  its  parts  are  simply 
enlarged  or  reduced  according  to  some  ratio, 
as  is  apparent  from  Fig.    18.     The  known 
quantities  are  the  change  in  the  tangent  x' 
(or  a?"),   the  central  angle  A  and  the  original 
radius  R. 


YV'  = 


Y'A 


sinZ/VV 


X' 

sin  A 


(12) 


Then  the  new  tangent  distance  A V  =  ^^ 
+  VY'.  The  triangle  BmB',  being  similar 
to  the  triangle  AO'  B',  is  isosceles  and  Viiii 
=  B'm.     Then  the  new  radius 


Fig.  17. 


R'  =  R  +  mB  =  R  + 


B'. 


vers  B'/;vB 


=  R4 


vers  A 


(13) 


RAILROAD  ENGINEER IX(; 


29 


Tlie  niodiiications  of  this  solution,  when  the  tangent  is  moved 
toward  the  center,  are  very  simple  and  are  apparent  from  the  figure. 

(.?)  To  change  the  directioii  of  the  forward  tangent  at  the 
point  of  tangencxj.  The  central  angle  scaled  off  from  the  paper 
location  miglit  have  an  error  which 
would  be  best  corrected  by  this  means. 
This  solution  is  but  one  of  a  large  class 
in  which  the  central  angle  is  modified. 
The  required  change  (a)  in  the  central 
angle  is  one  of  the  given  quantities. 
R,  A,  AV  and  BV  are  also  known. 
In  Fig.  19,  A'  =  A  -  a;  B-?  =  R  vers 
A ;  B.9  =  R'  vers  A' 


R'=R 


vers  A 


vers  (A  -  a) 
Also,  since  A.?  =  R  sin  A  and  A'-y 


(14) 


Fig.  18. 


R'  sin  A',  we  have 


AA' 


A.S'  =  R'  sin  A'  -  R  sin  A 


(•5) 


30.  Examples.  1.  Given  a  4"  20'  curve  w^th  a  central  angle 
of  18°  28'.  It  is  required  to  move  the  forward  tangent  parallel  to 
itself  12  feet.  How  much  is  the  change  of  the  P.O.  (the  distance 
A  A'  in  Fig.  17)  ? 

2.  Given  the  same  curve  as  above,  it 
is  required  to  move  the  tangent  tovKird  the 
center  12  feet,  but  without  changing  the 
P.O.  What  wnll  be  the  changes  in  the 
tangent  distance  and  the  radius? 

3.  Given  the  same  curve  as  above,  it 
is  required  to  diminish  the  central  angle 
by  0°  22',  but  retaining  the  same  P.T. 
What  will  be  the  new  radius  and  the  change 
in  the  P.O.? 


Fig.  19. 


COMPOUND   CURVES. 

31.  Definition.  Compound  curves  consist  of  a  succession  of 
two  or  more  curves  of  diflFerent  radii  which  have  a  common  tan- 
gent  where  they  meet.     They  maxj  be  laid  out  by  the  same  method 


30 


RAILROAD  ENGTNEEKINO 


as  simple  curves,  but  there  are  certain  geometrical  relations  exist- 
ing between  the  parts  of  a  compound  curve  which  greatly  facili- 
tate the  ccrmjmtations,  especially  when  any  modifications  are 
required.  In  the  following  demonstrations  11^  and  R^  will  always 
represent  the  smaller  and  larger  radii  respectively,  no  matter 
which  succeeds  the  other.  A,  and  A.,  will  always  represent  the 
corresponding  central  angles.  Although  R^  is  always  larger  than 
Ii„  A2  may  or  may  not  be  larger  than  A,.  T2  is  always  adjacent  to 
the  larger  radius  H^  and  is  always  larger  than  T^. 

32.  Mutual  Relations  of  the  Parts 
of  a  Compound  Curve  of  Two  Branches. 
The  curve  is  illustrated  in  Fig.  20,  in 
which  AC  and  CB  are  the  two  curves 
with  radii  of  ll^  and  E.,  respectively. 
Therefore  by  the  above  definitions  the 
other  functions  are  as  indicated  in  the 
figure.  Produce  the  arc  AC  until  the 
angle  COj  x  =  A^.  Then,  by  similar 
triangles,  the  chord  Cx  produced  must 
intersect  B.  Also,  if  xt  is  drawn  parallel 
to  CO2,  it  will  equal  B^  and  the  angle 
Then  draw  A.9  and  xk  perpendicular  to  Oj  x. 


-e 

JTi^ 

9^ 

^ 

r-v 
\ 

\ 
\ 

/ 

."-^ 

Ri 

0? 

Fig.  20. 


xi^  will  equal  A^. 
Then 


BA:    —  xt  vers  xtR  =  (K^  -  R,)  vers  A2 

xs     =  AGj  vers  AOj.'Z?  =  li^  vers  A 

Am  =  AV  sin  AYm    =  Tj  sin  A 

A7n  =  Bk  -i-  xs 

T,  sin  A  =  Ej  vers  A  +  (E2  -  I^.)  vers  A,  (16) 


By  drawing  a  few  additional  lines  in  the  figure,  it  may  similarly 
be  proved  that 

T2  sin  A  =  R2  vers  A  -  (K,  -  E,)  vers  Ai      (17) 

By  algebraic  transformation  we  may  derive  from  equations  16  and 
17  the  following  useful  relations.  The  details  of  the  derivation  of 
these  equations  is  suggested  as  a  profitable  exercise  for  the  student. 


K  =  K,  +  ^^^ 


Ti  sin  A  -  Ej  vers  A 


vers  (A  -  A,) 


(18) 


RAILROAD  ENGINEERING 


31 


R.  = 


T,  sin  A  vers  A^  -  T2  sin  A  (vers  A  -  vers  A,) 

vers  Aj)  (vers  A  -  vers  A.J 


(■9) 


vers  Ao  vers  A,  -  (vers  A 

SS,     Modifications  of  Location.     As  in  §  29,  only  a   few  of 
the  most  common  modifications  will  be  here  illustrated. 

1.  To  move  the  forward  tangent 
imrallel  to  itself^  hut  without  changing 
the  radii.     From  Fig.  21  we  derive 

X  =  0,.9  -  O2V  =-  (R,  -  R,)  cos  A,  -  (R, 
-  R,)  cos  A/,  from  which 


cos  A./  =  cos  A.3  - 


R.-R, 


(20) 


Fig.  21. 


Fig.  21  shows  the  tangent  as  having  been 
moved  outward',  in  such  a  case  the  P.C.C. 
(which  means  the  "point  of  compound 
curvature  ")  is  moved  backward  along  the  sharper  curve.  If  it  is 
desired  to  move  the  tangent  toward  the  center,  the  required  equation 
may  be  found  by  transposing  A.^  and  A/  in  equation  20.  But  in 
this  case  the  sharper  curve  must  be  extended  and  the  P.C.C.  must 
be  moved  forvmrd. 

In  case  the  larger  radius  comes  first,  the  figure  is  apparently 
quite  different,  although  a  little  study  will  show  that  the  same 
principles  apply.     From  Fig.  22  we  derive 

X  ^  o;h'  -  o,H = (R,  -  R,)  cos  a;-  (R,  -  R,) 

cos  A,  from  which  we  have 


cos  A,'  =  cos  A,  + 


Ro-R. 


(21) 


Fig.  22  shows  the  tangent  as  having  been 
moved  outward ',  in  such  a  case  the  P.C.C. 
is  moved  forward  along  the  easier  curve 
which  is  extended.  As  before,  if  the  tan- 
gent is  moved  invmrd,  transpose  A,  and 
A/  in  equation.     The  P.C.C.  will  then  be 

moved  hacMoard  along  the  first  curve. 

(5)     To  change  the  radius  of  one  of  the  curves  without 

rfmnging   either  tangent.      The  requirements   will   be   apparent 


from 


a  "pauer"  solution.     In    Fig.  23  assume  that   the  longer 


32 


KAILIIOAD  ENGINEERING 


radius,  which  comes  first,  is  to  be  shortened  by  an  amount  equal 
to  6-0^.  The  new  center  O'  must  lie  somewhere  on  the  arc  whose 
center  is  O,  and  whose  radius  is  Oj^.  It  also  must  lie  on  a  line 
which  is  parallel  to  AY  and  distant  from  it  by  li./  which  is  equal 
to  ^s  -  P.Cy.C.  With  0/  as  center,  draw  an  arc  from  Oj  to  ni . 
With  O.^  as  center,  draw  an  arc  from  Oj  to  m.  It  may  be  proved 
that  inin'  is  parallel  to  AY.  Draw  the  line  Oi?i' perpendicular 
to  AO2. 


(22) 


r)%yi  =  (TI2  -  Rj)  vers  A.,;  m'/i  =  (R/  -  Rj)  vers  A./; 

vers  A./  =  j^^, — y>-(  vei'S  ^-^ 
[K,  -  R,) 

AA'  =  0,,i  -  0,/a'  =  (R,  -  11,)  sin  A,  -  (  R;  -  R,)  sin  A,'  (23) 

34.     Examples.     1.     A  5^  30'  cnrve  with  a  central  angle  of 
16°  22' has  a  tangent  distance  of    1800  feet  from   the  P.O.  to  the 

vertex.  At  the  P.C.C.  the  curve 
compounds  into  an  easier  curve. 
The  total  central  angle  is  30°  18'. 
What  is  the  radius  of  the  easier 
curve,  and  what  is  tangent  dis- 
tance ? 

Answer.  The  given  quantities 
are  R,  the  ^A^r^^/' radius,  Aj,  A,  and 
T, ;  the  required  quantities  are  R^ 
and  To.  By  substituting  the  known 
quantities  in  equation  18  and  then 
the  computed  valve  of  R,,  in  equa- 
tion 17,  the  required  quantities  are 
The  student  should  perform  this  numerical  work. 
A  2°  30'  curve  450  feet  long  runs  into  a  5°  30'  curve  260 
feet  long.  It  is  required  to  move  the  forward  tangent  in  6.4  feet, 
but  without  changing  either  radius.  Required  the  change  in  the 
P.C.C.  Comment.  The  solution  evidently  requires  the  indicated 
modification  of  equation  21.  It  should  be  noted  that  a  practical 
solution  always  requires  that  the  resulting  value  of  the  cosine  shall 
be  less  than  unity,  which  mt^ans  that  x  can  never  be  greater  than 
(R2  -  R,),   and  also  means  that   the  sum  of    the  cosines   of    the 


Fig. 


found. 


RAILROAD  ENGINEERING  33 

original  angle  and  its  modified  angle  shall  be  less  than  unity.  The 
linear  change  in  the  P.C.C.  may  be  found  by  the  formula 

Linear  change  =  (angular  change  in  degrees) 
X  (radius  of  curve)    X  -fcTi^o 

3.  Assume  the  same  curve  as  in  example  2,  but  that  it  is 
required  to  change  the  2°  30'  curve  to  a  2°  curve  without  changing 
the  tangents.  Comment.  Fig.  23  may  be  made  to  apply  by 
transposing  the  new  and  old  larger  radii,  and  their  corresponding 
central  angles.  Note  that  when  such  changes  are  made  in  equa- 
tion 22,  the  equation  is  unchanged.  The  effect  on  equation  23  is 
merely  to  change  the  algebraic  sign,  which  means  that  the  P.C.C. 
is  moved  hacl'ivard  instead  of  forward. 

4.  Draw  a  figure  corresponding  to  Fig.  23  but  showing  a 
change  in  the  smaller  radius  Ji^. 

TRANSITION  CURVES, 

35.  Transition  Curve  Systems.  General  Use.  When  a  train, 
or  any  other  mass,  is  in  motion  it  requires  a  definite  force  to  make 
it  move  in  a  curved  path.  If  the  two  rails  of  a  railroad  curve  are 
level  transversely,  this  centripetal  force  can  only  be  furnished  by 
the  pressure  of  the  w^heel  flanges  against  the  outer  rail.  To  avoid 
such  a  dangerous  pressure,  which  would  make  high  speed  imprac- 
ticable, the  outer  rail  is  made  higher  than  the  other.  But  it  is 
manifestly  impracticable  to  suddenly  raise  the  outer  rail  at  the 
beginning  of  a  curve  and  lower  it  as  suddenly  at  the  end  of  the 
curve.  There  must  be  a  "run -off"  of  considerable  length.  If 
this  run-off  were  placed  exclusively  on  the  tangent,  there  would 
be  an  objectionable  jar  because  the  cars  were  tipped  on  a  straight 
track  where  there  is  no  compensating  centrifugal  force.  If  the 
run-off  were  entirely  on  the  curve  there  would  be  a  jar,  because 
the  centripetal  force  would  not  become  fully  developed  at  the  be- 
ginning of  the  curve;  and,  therefore,  a  transition  curve  is  used  at 
the  beginning  and  end  of  the  curve.  The  transition  curve  is  one 
whose  rate  of  curvature  gradually  increases  from  nothing  to  the  rate 
of  the  central  part  of  the  curve.  If  the  super-elevation  of  the  outer 
rail  is  begun  at  the  beginning  of  the  transition  curve  and  is  grad- 


34  -  RAILROAD  ENGINEERING 

ually  increased  as  the  curvature  increases  so  that  the  proper  super- 
elevation is  attained  at  the  end  of  the  transition  curve  where  the 
regular  curve  commences,  then  the  theoretical  requirements  are 
satisfied.  But  there  is  another  important  reason  for  transition 
curves.  On  a  curve  the  bogie  trucks  of  a  car  make  an  angle  with 
the  axis  of  the  car.  If  there  were  an  instantaneous  change  from 
a  straight  track  to  the  full  degree  of  curvature  the  change  of  posi- 
tion of  the  truck  would  need  to  be  accomplished  in  the  time 
required  for  its  train  to  run  the  distance  between  the  truck  centers 
of  a  car.  For  a  high-speed  train  this  distance  would  be  covered 
in  less  than  a  second.  On  a  transition  curve  this  change  of 
position  is  accomplished  gradually  and  without  jar.  The  amount 
of  the  required  super-elevation  will  be  discussed  in  the  following 
sections. 

Varieties  of  Curves.  A  theoretically  exact  transition  curve  is 
very  complicated  and  its  mathematical  solution  very  difficult. 
Many  systems  of  curves  have  been  proposed,  all  of  which  are  objec- 
tionable for  some  one  of  the  following  reasons,  as  stated  in  a  report 
by  a  Committee  of  the  American  Railway  Engineering  Association. 
"(1)  If  simple  approximate  formulas  were  used  they  were  not 
sufficiently  accurate.  (2)  Accurate  formulas  were  too  complex. 
(3)  The  curve  could  not  be  expressed  by  formulas.  (4)  Formulas 
were  of  the  endless  series  class.  (5)  Complex  field  methods  were 
required  to  make  the  field  work  agree  with  formulas  with  spirals  of 
large  central  angles."  The  Committee  then  developed  a  method 
which  gives  results  whose  accuracy  is  beyond  that  of  the  most  care- 
ful field  work  and  yet  which  is  sufficiently  simple  for  practical  use. 
The  mathematical  development  is  too  elaborate  to  be  detailed  here 
but  the  working  formulas,  together  with  a  condensation  of  the 
Tables  will  be  given,  together  with  an  explanation  of  their  practical 
use  and  application,  with  examples. 

The  general  form  of  these  curves,  whatever  their  precise  mathe- 
matical character,  is  shown  in  Fig.  24.  AVE  are  two  tangents, 
joined  by  the  simple  circular  curve  ACB,  having  the  center  O. 
Assume  that  the  entire  curve  is  moved  in  the  direction  CO  a  distance 
00'  =  CC'  =  BB'  =  AA'.  At  some  point  TS  on  the  tangent,  the 
spiral  begins  and  joins  the  circular  curve  tangentiaUy  at  SC.  The 
other  spiral  runs  from  CS  to  ST.    The  significance  of  these  symbols 


RAILROAD  ENGINEERING 


35 


may  be  readily  remembered  from  the  letters;  T,  S,  and  C  signify 
tangent,  spiral,  and  circular  curve;  T^  is  the  point  of  change  from 
tangent  to  spiral,  SC  the  point  of  change  from  spiral  to  curve,  etc. 
At  the  other  end  of  the  circular  curve,  the  letters  are  in  the  reverse 
order,  the  station  numbers  increasing  from  A  to  B.  The  meaning 
of  each  of  the  various  symbols  used  is  plainly  indicated  on  the 
diagram,  Fig.  24. 

The  length  of  a  spiral  can  only  be  computed  on  the  basis  of 
certain  assumptions  as  to  the  desired  rate  of  tipping  the  car,  so  as 
to  avoid  discomfort  to  passengers,  and  of  course  this  depends  on  the 
expected   velocity.     There    is 
also    a    limitation    since   the 
sum  of  the  two  spiral  angles 
cannot  exceed  the  total  cen- 
tral angle  of  the  curve.     The 
7n  in  im  nm     lengths     recom- 
mended are  as  follows: 
On    curves    which   limit  the 
speed : 


6°  and  over,  240  feet 
less  than  ()°,  5^  X speed  in 

m.p.h.  for  elevation  of  8 

inches 


On  curves  which  do  not 
the  speed : 


limit 


Fig.  24. 


30  times  elevation  in  inches,  OR 

fX ultimate  speed  in  m.p.h.  X  elevation  in  inches 


For  example.  (1)  5°  curve  which  limits  speed;  speed  limit  48 
m.p.h.  by  interpolation  in  table,  §41;  48X5J=256  feet  minimum 
length.  (2)  3°  curve;  maximum  operating  speed  60  m.p.h.;  super- 
elevation .62  feet  =  7.44  inches;  30X7.44=  223.2  feet;  OR,  §X60 
X7.44  =  297.6  feet.  Of  course  the  higher  value  should  be  used,  or 
say  300  feet  as  the  minimum  length.  While  it  is  generally  true 
that  the  longer  transition  curves  give  easier  riding,  the  spiral  must 


36  •  RAILROAD   ENGINEERING 

not  reach  the  center  point  of  the  curve.  Since  it  is  approximately 
true  that  the  spiral  extends  for  equal  distances  on  each  side  of  the 
original  point  of  curve,  it  is  nearly  true  that  two  spirals,  each  having 
the  same  length  as  the  original  curve,  would  meet  at  the  center. 
The  length  of  a  spiral  should  in  general  be  far  less  than  the  length 
of  the  original  curve. 

36.  Symbols.    Besides  the  symbols  whose  significance  is  clearly 
indicated  in  Fig.  24,  the  following  are  defined : 

a — ^The  angle  between  the  tangent  at  the  TS  and  the  chord 
from  the  TS  to  any  point  on  the  spiral. 

A — ^The  angle  between  the  tangent  at  the  TS  and  the  chord 
from  the  TS  to  the  SC. 

.    b — The  angle  at  any  point  on  the  spiral  between  the  tangent 
at  that  point  and  the  chord  from  the  TS. 

B — The  angle  at  the  SC  between  the  chord  from  the  TS  and 
the  tangent  at  the  SC. 

D — The  degree  of  the  central  circular  curve. 

A — The  central  angle  of  the  original  circular  curve,  or  the 
angle  between  the  tangents. 

<^ — ^The  central  angle  of  the  whole  spiral. 

<^i — The  central  angle  of  the  spiral  from  the  TS  to  the  first 
spiral  point. 

k — ^The  increase  in  the  degree  of  the  curve  per  station  on  the 
spiral. 

L — ^The  length  of  the  spiral  expressed  in  feet  from  the  TS  to 
the  SC. 

s — ^The  length  of  the  spiral  in  stations  from  the  TS  to  any  given 
point. 

S — ^The  length  of  the  spiral  expressed  in  stations  from  the  TS  to 
theSC. 

37.  Deflections.    The  field  formulas  for  deflections  are  based 
on  the  following  two  equations 

a  =  10ks^  minutes  =  —01  f 

o 

a  =  lOA-S^  minutes = -—(f) 

o 

The  first  deflection  ai  =  10ksi^  minutes.    But  k  is  the  increase  in 


RAILROAD  ENGINEERING  37 

degree  of  curve  per  station  and  since  the  degree  of  curve  increases  as 
the  length  A:  =  D-^S,  S  being  expressed  in  stations.     For  point  1, 

since  8  =  10^,  ai  =  10  (  —  \s^  =  T>s,  which  may  be  expressed  as  the 

\10s/ 

degree  of  curve  times  the  length  of  the  chord  in  stations.  For 
example,  if  the  spiral  is  400  feet  long  (L  =  400  and  S=4)  and  runs 
on  to  a  5°  curve  (D  =  5),  one  chord  is  40  feet  long  or  s  =  A  stations. 
Then  ai  =  5X0.4  =  2  minutes  of  arc  for  the  deflection  for  the  first 
chord  point.  And  since  the  deflections  are  as  the  square  of  the 
number  of  stations,  the  deflections  from  TS  to  succeeding  stations 
will  be  4,  9,  16,  25,  36,  49,  64,  81,  and  100  times  2  minutes,  as  shown 
in  the  second  vertical  column  of  Part  A  of  Table- IV.  The  last 
deflection  A  =  100x2' =  200' =  3°  20'  =  J  (10°)  =i</>,  which  is  the 
total  central  angle  of  the  spiral.  This  result  also  checks  the  general 
equation 

"^      2"        2      20000    200 
Since 

DS_5X4 

The  deflections  from  any  point  of  the  spiral  to  any  other  point, 
either  forward  or  backward,  may  be  found  by  multiplying  the  value 
of  a  I  (in  this  case  2')  by  the  coefficients  in  the  proper  vertical  column 

U  V 

of  that  table.     The  values  of  the  ratios  —  and  —  for  even  degrees 

C    X  Y 

and  for  A,  — ,  ^,  and  —  for  half  degrees  are  given  in  Parts  B  and 

C,  Table  IV. 

38.  Insertion  of  a  Spiral  between  a  Tangent  and  a  Circular 
Curve.  In  Fig.  25  it  has  been  necessary  to  make  the  distance 
MM'  about  100  times  its  real  proportional  value  in  order  to  make 
the  illustration  distinct.  The  curve  AMB  is  a  simple  circular 
curve  joining  the  two  tangents,  such  as  would  be  used  without 
spirals.  If  a  suitable  spiral  is  started  at  a  suitable  point  Q,  and 
run  to  some  point  Z,  such  that  the  total  central  angle  of  the  spiral, 
<f),  equals  the  angle  ZO'N  of  the  curve,  and  then  the  circular  curve 
having  a  common  tangent  with  the  spiral  at  Z,  is  run  to  Z',  from 


38 


RAILROAD  ENGINEERING 


Fig.  25. 


m  =  MM'  =  AA'  =  BB'  = 


which  a  similar  spiral  is  run  to  the 
tangent  at  Q',  such  a  combination  of 
curves  will  give  the  desired  result.  It 
is  now  necessary  to  compute  the  di- 
mensions required  to  accomplish  this 
result.  The  introduction  of  the  spiral 
has  the  effect  of  throwing  the  curve 
away  from  the  vertex  by  the  amount 
MM',  which  we  will  call  m;  it  also  re- 
duces the  central  angle  of  the  circular 
curve  by  2(f).  ZK  is  the  y  ordinate 
of  the  chosen  spiral  and  QK  the  x 

ordinate. 

A'N  =  ?/-Rvers0. 

Therefore, 

A'N       2/— R  vers  0 


cos 


cos 


|A 


(24) 


NA  =  AA'sinyA 
VQ  =  QK-KN+NA4-AV 


1 


(i/— R  vers  <^)  tan  —A 


=  .T— R  sin  (f)-\-(y  —  'R  vers  </>)  tan  — A+R  tan— A 
=  .T  — R  sin  4)-\-y  tan  —A+R  cos  (j)  tan  —A 

^1  Zd 


(25) 


As  a  numerical  solution  of  any  problem  will  usually  involve  the 
determination  of  the  value  of  A'N,  equation  25  may  be  reduced 
from  four  terms  to  three  as  follows :  Transform  the  equation  above 
equation  25  to  read 


VQ  =  a:+R  (tan-^A 


sin  </))+A'N  tan— A 
y         R  vers  <^ 


cos 


COS 


VM'  =  VM+MM'  =  R  exsec  -^A 
AQ  =  VQ  — AV  =  .T— R  sin  (^+  (</-R  vers  <^)  tan  — 


iA 


(26) 
(27) 
(28) 


39.     Example.     It   is   required   to   join   two   tangents   which 
make  an  angle  of  28°  16'  by  a  6°  curve  terminated  by  suitable  spirals. 
Assume  a  10-chord  spiral  240  feet  long.     Then 
DL^6X240^ 
'^    200       200 


RAILROAD  ENGINEERING 


39 


From  Part  C,  Table  IV,  when  0  =7.2° 

^  =  .998517 --^(.998517  -  .998298)  =  .998430 
L  o 

X  =  .998430  X  240  =  239.623 

^  =  .040681  +—  (.043581  -  .040681)  =  .041841 
L  o 

¥  =  .041841X240  =  10.042 

1 


yA  =  14°8' 

Logarithms 

(Equation  24) 

R 

2.98017 

Y     10.042 

vers  7°  12' 

7.89682 

- 

7.533 

0.87699 

(Equation  27) 


A'N    2.509  1 

cos -A 


0.39950 
9.98665 


m  =  MM'  =  AA'  =  2.587  0 .  41285 

R  2.98017 
1 

exsec— ^  8.49436 

1.47453 


VM  =  29.821 

m=  2.587 
VM'  =  32.408 


(Equation  26) 


a:  =  239. 623 
.    120.825 


0.632 


nat.  tan.  —A  =0.25180 
nat.  sin  <^  =  0.12533 


(see  above) 


VQ  =  361.080 
(Equation  28) 

240.564 
AQ  =  120.516 


0.12647 

9.10198 

R 

2.98017 

2.08215 

A'N 

0.39950 

tan-l-A 

9.40106 

AN_ 

9.80056 

R 

2.98017 

tani-A 

9.40106 

AV 

2.38123 

40 


RAILROAD  ENGINEERING 


Pig.  26. 


40.  Insertion  of  Spirals  in  Old  Track.  Au  engineer  fre- 
quently has  occasion  to  insert  spirals  in  track  which  was  not  so 
laid  out.  The  simplest  method  from  a  mathematical  standpoint 
is  that  given  in  the  two  previous  sections.  But  this  would  involve 
moving  the  whole  track  for  the  entire  length  of  the  curve,  and 
also,  since  it  is  apparent  from  Fig.  25  that 
the  new  line  QZZ'Q'  is  shorter  than  the  old 
line  QAMBQ',the  method  will  involve  rail 
cutting  and  the  boring  of  holes  for  track 
bolts.  The  following  method  makes  a 
slight  sharpening  of  cui-vature  of  the  mid- 
dle circular  section,  which  at  the  center  is 
slightly  outside  of  the  old  track,  and  so 
crosses  the  old  line  that  the  lateral  devi- 
ation from  the  old  line  is  always  very 
small  and  the  length  of  the  new  track 
need  not  differ  appreciably  from  that  of 
the  old.     The  method  of  solution  is  indicated  in  Fig.  26. 

O'N  =R'  cos  <;^  +  2/     (This  shows  more  clearly  in  Fig.  25.) 
OT=0'Nseci-A 

=  R'  cos  <f)  sec  -—A  -\-y  sec  -^r^r 

m=MM'=MV-M'V 
=  R  exsec  —A  -R'  cos  0  sec  —A  -^  sec  —  A+R'       (29) 

AQ  =  QK-KN+NV-VA 

=  x-W  sin  0  +  (R'  cos  0  +  7/)  tan  -^A-R  tan  -i-A 

=  x-W  sin  <^  +  R'  cos  0  tan  -1a-(R-z/)  tan  -^A      (30) 


The  length  of  the  old  line  from  Q  to  Q'  =  2AQ+100 


D* 


The  length  of  the  new  line  from  Q  to  Q'  =  2L+ 100  ^— ?^> 
in  which  L  is  the  length  of  each  spiral. 


(31) 


RAILROAD  ENGINEERING 


41 


41.  Example.  Assume  that  a  track  has  been  laid  with  a  6° 
curve  for  39°  50':  It  is  desired  to  insert  suitable  spirals  without 
altering  the  length  of  the  old  track.  Solution.  Unfortunately 
there  is  no  method  of  solving  this  problem  so  as  to  obtain  directly 
the  revised  value  for  the  radius:  The  new  radius  will  always  be 
about  5  per  cent  shorter  than  the  old.  The  larger  the  central  angle, 
the  less  will  be  the  difference.  The  only  method  is  therefore  to 
assume  a  value  for  R',  solve  equation  30,  and  then  compare  the 
lengths  of  the  new  and  old  lines.  If  the  difference  is  so  small  that 
it  may  be  neglected,  the  problem  is  solved.  If  not,  a  slight  modi- 
fication of  the  new  radius,  such  as  experience  in  these  computations 
will  suggest,  will  usually  give  on  a  second  trial  a  value  which  is 
sufficiently  close.  As  a  first  trial  for  the  above  numerical  case,  wp 
will  assume  a  6°  20'  curve  for  the  new  curve,  and  a  240  ft.  spiral 
whose  0  =  7°  36'.     rr  =  239.580  and  ?/  =  10.60. 

Logarithms. 

X  =  239 .  580  R'  (6°  20')     2 .  95671 

sin  7°  36'    9.12141 

119.709 


325.069 


564.649 
462.019 


342.310 
462.019 


2.07812 

R' 

2.95671 

cos  7°  36' 

9.99617 

tani-A 

9.55909 

2.51197 

R  =955.37 

y=   10.60 

944.77 

2.97532 

tan  —A 

9.5590'9 

2.53442 


AQ  =  102.630 
The  length  of  the  old  curve  from  Q  to  Q'  is 
100  A, 10^39.83333^ 
D  6 

2AQ=  2X102.630  = 


663.889 

205.260 
869.149 


42  RAILROAD  ENGINEERING 


The  length  of  the  new  curve  from  Q  to  Q'  is 

100^=100§i:f|=l^=  388.947 


2L  =  2  X  240  =  480.000 


868.947  868.947 


Difference  in  length  =     0 .  202 

When  it  is  considered  that  in  that  length  of  869  feet  there  will 
be  about  27  rail  joints  and  that  a  stretching  at  each  joint  of  about 
.0075  foot  will  make  up  for  this  difference  of  length,  it  might  not 
be  necessary  to  cut  the  rails. 

To  illustrate  the  method  of  adjustment  if  a  more  accurate 
value  for  R'  were  required;  note  that  in  the  above  case  the  new 
curve  is  too  short.  If  R'  is  diminished  (say  from  D'  =  6°  20'  to  D 
=  6°  24'),  one  term  of  equation  30  will  be  increased  and  one  of  them 
diminished,  but  the  net  change  in  the  value  of  AQ  is  3 .  403,  which 
will  decrease  the  length  of  the  old  curve  by  6 .  806.  But  such  a  change 
in  D'  will  decrease  the  length  of  the  new  line  by  6 .  552. 

The  revised  length  of  the  old  line  is,  therefore,  862.343  and 

the  revised  length  of  the  new  line  is  862 .  395 

The  revised  difference  is    0.052 

The  new  line  is  now  longer  than  the  old,  but  the  difference  is  insig- 
nificant (about  one  fortieth  of  an  inch  per  joint).  By  interpolation 
D'  =  6°  23'  is  the  better  value  to  use. 

There  is  another  method  of  introducing  a  spiral  into  old 
track  without  even  changing  the  central  part  of  the  curve.  The 
spiral  runs  into  a  curve  which  is  sharper  than  the  original  curve 
which  then  compounds  into  the  old  curve.  The  solution  of  this 
method  consists  in  so  choosing  and  locating  the  spiral  and  the 
sharper  curve  that  it  will  compound  into  the  original  curve.  The 
details  of  this  method  will  not  be  here  given  because,  although  it 
involves  less  track  work  at  the  start,  it  is  a  more  complicated 
alignment  to  maintain  and  the  method  is  inferior  to  the  one  pre- 
viously given- 


RAILROAD  ENGINEERING  43 

On  the  basis  of  D'  =  6°  20' 
(Equation  29) 


Logarithms. 

R(6°) 

2.98017 

1  . 
exsec  —A 
2i 

8.80356 

60.776 

1.78373 

905.13 

965.906 

R' 

cos  <i> 

1 . 

secyA 

2.95671 
9.99617 

0.02678 

954.255 

loga!  = 

2.97966 

1.02530 

11 

.274 

1  . 
secyA 

0.02678 

1.05209 

965.529 

965.529 

m=     0.377  foot 

Note  that  the  maximum  lateral  change  in  the  track  is  less  than  five 
inches. 

On  many  railroads  where  there  has  been  no  pretense  to  using 
spirals  the  track  foremen  have  produced  nearly  the  same  result  in 
a  rough  uncertain  way  by  throwing  in  the  curve  somewhat  near 
the  point  of  curve.  This  necessarily  sharpens  the  curve  further 
on,  and  thus  substantially  the  same  result  is  obtained  as  is 
described  above  but  without  any  calculations  or  any  theoretical 
accuracy.  It  is  only  by  such  means  that  a  tolerable  riding  track 
can  be  produced  when  transition  curves  are  not  used. 

42.  yjsQ  of  Transition  Curves  with  Compound  Curves.  It 
is  shown  in  the  last  few  sections  that  the  lateral  deviation  involved 
by  the  use  of  spirals  is  very  small.  Since  compound  curves  are 
usually  employed  only  when  the  location  is  difficult,  it  is  best  to 
make  the  calculations  as  if  no  spirals  were  to  be  used,  except  that 
approximate  allowances  may  be  made  for  such  lateral  changes  as 
will  be  required.  Then  the  changes  can  be  computed  as  follows. 
Theoretically  there  should  be  a  transition  curve  between  the  two 
branches  of  a  compound  curve,  but  when  a  train  is  already  on  a 
curve  and  the  wheels  are  pressing  against  the  outer  rail,  it  will 
cause  but   little  jar  to  merely  increase  the  curvature.     The  intro- 


44 


RAILROAD  ENGINEERING 


duction  of  such  spirals  will  not  be  here  given.  Transition  curves 
need  not  be  used  in  running  on  to  curves  which  are  easier  than 
3°  and  even  4"".  Therefore  if  one  branch  of  a  compound  curve  is 
of  easy  curvature,  as  is  frequently  the  case,  it  will  not  bie  neces- 
sary to  use  a  spiral  at  that  end  of 
the  curve.  Therefore  two  cases 
will  be  developed — using  spirals  at 
one  end  only,  and  at  both  ends. 

(r/)     jSplral  at  one  end  onltj. 
The  method  of  §38  may  be  adopted 


La   hSO*--^!     ^O 


by  substituting  Aj  for  ^  A  in  equa- 
tions 24  to  28.  This  would  move 
the  P.C.C.  from  M  to  M'.  But 
since  the  two  curves  must  be  made 
to  coincide,  the  sharper  curve  will 
be  moved  parallel  to  the  tangent 
BV  a  distance  of  M'M,  while  the 
unchanged  circular  curve  will  be  moved  parallel  to  the  tangent 
AY  a  distance  MM^.     Calling  MM'  =  m^,  we  have.  Fig.  27, 


% 


Fig.  27. 


M 
MM 


cos  A. 


^mr   sin  M/MM,             sin  (90°  -  A„) 
/M,  =  MM/  .*       ',^.    '  =  m, ^ — T — ^  =  m,  -. — ^ 


sin  M;  M,M 


cos  A, 


m. 


sin  A 


(32) 


It  should  be  noted  that  the  new  P.O.  is  at  A'  and  that  AA'  = 
MM*,  while  the  P.T.  is  changed  from  B  to  Q/,  which  equals  BQj  - 
QQ'.  BQ,  is  found  from  equation  28  and  Q/Qi  =  Mi'M4  is 
found  from  equation  32. 

(b)     Spiral  at  hotk  ends.     Applying  the  method  of  §38  to 
each  branch  of  the  curve  in  turn  by  successively  substituting  A, 

and  A^  for^  A,  we  will  obtain  values  for  m^  and  m.^  which  will  in 

general  differ  considerably.  But  as  before  we  may  move  each 
revised  curve  as  shown  in  Fig.  28  and  as  computed  in  equations 
34  and  35,  Calling  MM,'  =  m^  and  MM/  =  vi^,  and  noting 
chat  the  angle  at  M,'  (see  the  detail)  =  90°  -  A,,  the  angle  at  M/ 


RAILROAD  ENGINEERING  45 

==  90°-  A_,  and  the  angle  at  M3  =  A,  we  have   the   following: 


M/M3 


^r  ,^r    sin  (90^  -  A,)      ^  ,  cos  A,        .      . 


sin  A 


sin  A 


m;m3  ==  M/M 


^  sin  (90°  -  A,) 
'  sin  A 


=  (v/^i  -  m,) 


cos  A, 


sin  A 


(35) 


As  in  the  previous  case,  the  position  of  the  new  point  of  the  spiral 
is  found  in  each   case  from  one  of  the   above   quantities   and  the 
change  computed   from  equation  28.     Note  that  in  one  case  the 
point  of  spiral  is  moved 
nearer  to,  and  in  the  other 
case  further   away  from, 
the  vertex. 

43.  Example.  Given 
a  7°  20'  curve  for  29°  40' 
followed  by  a  4°  10'  curve 
for  25°  20'.  Required  to 
introduce  suitable  spirals. 
Using  equation  24  suc- 
cessively with  the  two 
sets  of  figures  w^e  obtain 
mi  =  5.506  and  ?ri2=  1.930. 
Then  {jni  —  m2)  =  3.576. 
Substituting  this  value  in 
equations  34  and  35  we 
obtain  Ml  Ms  =  3.946  and 
Ms'Ms    =    3.793.     Using 

equation  28,  calling  —A  = 

25°  20',  we  compute  AQ2  =  120.769.  But  we  must  add  to  this  an 
amount  equal  to  Mz'Ma  =  3.793,  which  makes  AQ2'  =  124.562.  Simi- 
larly, calling —A  =  29°  40'  in  equation  28,  we  may  compute  BQi  = 

152.444.  But  from  this  must  be  subtracted  M/M3  =  3.946,  which 
makes  BQ/  =  148.498.  The  actual  lateral  change  from  the  original 
point  M  is  equal  to  MMo'+Ms'Ms  sin  A2  =  1.930+1.623  =  3.553. 
The  student  should  verify  in  detail  all  these  calculations. 


Fig.  28. 


46  RAILROAD  ENGINEERING 

44.  Field  Work.  \Yhen  spirals  form  part  of  the  original 
location,  it  is  a  useless  refinement  to  locate  all  the  chord  points 
before  earth  work  has  been  done.  It  is  then  sufficient  to  locate  the 
beginning  and  end  of  each  spiral  with  perhaps  one  intermediate 
point  in  case  the  spiral  is  very  long.  During  the  resurvey  which 
immediately  precedes  track  work,  when  the  roadbed  is  graded  and 
flat,  the  intermediate  points  are  readily  inserted.  Referring  to 
Fig.  25,  the  point  Q  (or  TS)  would  first  be  located  at  a  distance  VQ 
(see  equation  25)  from  the  point  V.  Assume,  as  in  Fig.  25,  a  simple 
curve,  6°,  with  A  =  32°,  and  at  each  end  a  spiral  240  feet  long.  Dur- 
ing the  first  location  of  the  road  it  would  be  sufficient  to  locate  the 
end  of  the  spiral  at  point  Z  or  SC.     The  deflection  from  the  tangent 

when  the  instrument  is  at  TS  and  is  ''sighting  at"  SC  is  — 0  =  -;- 

o  o 

(M)  ^jQl^)  ^-°  •*  =  2°24'.  The  ordinate  X  (QK  in  Fig.  25) 

is  239.623  and  the  distance  out  from  the  tangent  KZ  =  z/  =  10.042. 
The  total  central  angle  to  this  point  (</))=7°  24'.  The  central 
angle  left  between  Z  and  Z'  =  32°-(2x7°  240  =  17°  12'.  Set  up 
the  instrument  at  Z.  The  deflection  from  the  tangent  at  the  point 
occupied  when  the  instrument  is  at  Z  (which  is  here  SC)  and  is 
sighting  at  Q  or  TS  is  B=  §0  =  4°  48'.  Setting  off  that  deflection 
on  the  transit  so  that  when  the  instrument  is  turned  around  to  the 
tangent  it  shall  read  0°,  the  remaining  central  angle  of  17°  12'  can 
be  laid  off  in  the  usual  manner.  Again  setting  up  the  instrument 
at  Z'  (which  is  point  CS  of  that  spiral)  the  point  Q'  or  ST  is  located 
with  the  same  deflection  (4°  48')  as  the  back  sight  from  Z  to  Q. 
The  distance  from  Z'  to  the  tangent  VQ'  is  likewise  the  same  as 
ZK  =  10.042. 

When  the  intermediate  points  are  to  be  located,  the  transit  is 
set  up  at  Q  and  the  points  are  located  by  chord  lengths  of  24  feet 
and  with  deflections  to  the  various  points  as  given  by  multiplying 
tti  (which  =6 X. 24  =1.44  minutes  of  arc)  by  the  factors  in  the 
column  under  TS.  W^hen  the  circular  curve  ZZ'  has  been  located 
and  the  transit  set  up  at  Z'  and  oriented  so  that  it  will  read  0°  when 
sighting  along  the  tangent  to  the  curve  at  Z',  then  (using  the  deflec- 
tion factors  in  the  column  under  SC)  the  deflection  to  the  point 
9,  24  feet  away,  is  29X1.44' =  41.76';  to  the  next  point  8  it  is  56X 


RAILROAD  ENGINEERING        ^  47 

1.44'  =  80.64' =  r  20.64';  the  points  7,  6,  etc.  are  found  similarly; 
to  the  point  of  tangency  Q  it  is  200X1.44' =  288' =  4°  48',  as  given 
before.  Then  the  transit  should  be  set  up  at  Q'  and  back-sighted 
on  Z'  with  a  reading  of  2°  24'.  If  the  vertex  of  the  curve  V  had 
already  been  previously  located  and  the  field  work  is  accurate,  the 
sighting  on  V  should  be  0°.  Also  the  reading  on  any  other  point  of 
the  spiral  may  be  computed  from  the  column  of  coefficients  under  TS. 

It  sometimes  becomes  necessary  to  set  up  the  transit  at  some 
intermediate  point"  of  the  spiral,  as  the  point  3.  With  the  instru- 
ment set  up  at  3,  use  the  coefficients  under  the  column  3^  in  the 
table,  orienting  the  transit  by  a  sighting  at  any  known  point  with 
the  transit  set  at  the  given  deflection  for  that  point.  Then,  when 
the  telescope  is  turned  to  0°,  the  transit  will  be  sighting  along  the 
tangent  to  the  curve  at  the  point  3  and  the  deflection  to  any  other 
point,  forward  or  backward,  will  be  as  given  in  that  column  by  the 
coefficient  times  ai. 

It  may  be  noted  that  the  deflections  are  given  to  fractions  of  a 
minute  of  arc,  which  is  of  course  very  much  closer  than  an  ordinary 
transit  can  be  used.  But  the  location  of  spirals  demands  the  closest 
work  attainable  with  the  ordinary  field  transit;  and  even  though 
the  transit  is  only  graduated  to  single  minutes,  a  fraction  of  a  minute  y 
can  be  estimated  when  setting  the  vernier  of  a  good  transit  and 
therefore  the  precise  angles  are  given  so  that  the  blosest  attainable 
value  of  the  true  angle  m-ay  be  set  off. 

VERTICAL  CURVES, 
45.  Reasons  tor  Use.  Although  the  change  of  direction  of 
motion  due  to  a  change  of  grade  is  never  as  great  as  that  of  an 
ordinary  horizontal  curve,  yet  it  is  as  necessary  in  one  case  as  in 
the  other  to  join  the  two  grade  lines  by  a  "  vertical  curve."  As 
in  the  case  of  horizontal  curves,  there  is  nothing  which  absolutely 
determines  the  rate  of  curvature.  When  the  grades  intersect  over 
a  summit  a  comparatively  short  curve  is  permissible,  but  when 
passing  through  a  sag  the  upward  bend  of  the  track  acts  as  a 
literal  obstruction  and  therefore  a  much  longer  curve  is  necessary. 
Some  roads  adopt  some  uniform  distance,  such  as  200  feet  each 
side  of  the  vertex,  as  the  length  of  all  such  curves,  regardless  of 
the  change  in   the  rate  of  grade.     A  more  logical  method  is  to 


48  •  RAILROAD  ENGINEERING 

make  the  length  a  function  of  the  change  of  grade.  A  very  com- 
mon rule  is  to  make  the  length  100  feet  for  each  tenth  of  one  per 
cent  of  change  of  grade.  For  example,  a  one  per  cent  grade 
descending  into  a  hollow  is  followed  by  a  1.2  per  cent  grade  climb- 
ing out  of  it;  what  should  be  the  length  of  the  vertical  curve  at 
the  sag?  The  change  of  grade  is  the  numerical  sum  of  the  grades 
or  2.2  per  cent;  therefore,  by  the  above  rule  the  length  should  be 
2,200  feet.  Such  a  length  is  excessive,  but  such  a  change  of  grade 
is  also  somewhat  unusual  and  hardly  to  be  found  where  the  speed 
was  high.  For  lower  speed  such  a  long  vertical  curve  is  not 
essential. 

46.  Qeometrical  Form  of  the  Curve.  The  method  of  lay- 
ing out  such  a  curve  is  illustrated  in  Fig.  29,  in  which  the  grades 
are  exaggerated  enormously.     The  curve  begins  and  ends  at  equal 

distances  on  each  side 
tri ^ Z^^^^''^^     ^^  ^^^  vertex  B,  as  at 

^y^**-*^^,,^^^  \  ^^^^  ure  join  A  and  C;  bi- 

B  sect  AC  at  6,  join  B 

Fig.  29.  and  e  and  bisect  B^  at 

//.It  may  be  proved 
mathematically  that  a  parabola  may  be  passed  through  h  and  tan- 
gent to  AB  and  BC  at  A  and  0,  and  also  that  at  a/??/ point,  as  at  w, 
the  distance  to  the  tangent  (67?)  is  proportional  to  the  square  of  the 
distance  from  A.     Expressing  this  statement  algebraically,  we  have 

But  since,  in  any  given  case  eh  is  a  constant  and  (A^)^  is  a  con- 
stant,  we  may  say  for  any  one  curve  that  the  correction  from  the 
straight  grade  line  to  the  curve  equals  a  constant  times  the  square 
of  the  distance  from  one  end  of  the  curve. 

47.  Numerical  Example.  Assume  that  the  intersection  of 
the  grades  B  comes  at  Sta.  15  +  40;  that  the  grade  AB  is  -  0.6 
per  cent  and  the  grade  of  BC  is  +  0.8  per  cent.  Then  if  we 
adopt  the  rule  of  100  feet  for  each  tenth  per  cent  of  change,  the 
curve  must  be  1,400  feet  long,  must  begin  at  Sta.  8  +  40  and 
extend  to  Sta.  22  +  40.      Assume  that  the  elevation  of   B  is 


RAILROAD  ENGINEERING  49 

152.50;  then  the  elevation  of  A  is  152.50  +  (7  X  0.6)  =  156.7. 
Similarly  the  elevation  of  C  is  computed  as  158.1.  Then  the  ele- 
vation of  e  is  the  mean  of  these  two,  or  157.4.  B^  is  therefore 
=  4.9  and  eh  =  2.45.  Then  eh  ^  (Aef  =  2.45  -i-  490000  = 
.000005,  the  constant  which  is  to  be  multiplied  by  the  square  of 
the  distance  from  A  to  obtain  the  correction  from  the  straight 
grade  up  to  the  curve.  The  elevations  of  the  several  stations  is 
most  readily  calculated  in  a  tabular  form  such  as  is  given  below. 

A.  Station 

8  -h  40,elev.  =  152.50  +  (7  X  0.6)  '         =  156.70 

9  =  156.70 -(0.6  X  0.6)  +  .000005  X    60^  =  156.36 

10  =  156.70-  (1.6  X  0.6)  +  .000005  X  160^  =  155.87 

11  =  156.70 -(2.6  X  0.6)  +  .000005  X  260^  =  155.48 

12  =  156.70-  (3.6  X  0.6)  +  .000005  X  360^  ==  155.19 

13  =  156.70  -  (4.6  X  0.6)  +  .000005  X  460^  =  155.00 

14  =  156.70 -(5.6  X  0.6)  +  .000005  X  560^  =  154.91 

15  =:  156.70  -  {6.6  X  0.6)  +  .000005  X  660^  =  154  92 

B.  Station 

15+40,  elev.  =  152.50  +  2.45  =  154.95 

16  r=  158.10 -(6.4  X  0.8)  +  .000005  X  640^  =  155.03 

17  =  158.10 -(5.4  X  0.8)  +  .000005  X  540^  =  155.24 

18  =  158.10-  (4.4  X  0.8)  +  .000005  X  440^  =  155.55 

19  =  158.10-  (3.4  X  0.8)  +  .000005  X  340^  =  155.96 

20  =  158.10  -  (2.4  X  0.8)  +  .000005  X  240^  =  156  47 

21  =  158.10  -  (1.4  X  0.8)  +  .000005  X  140^  =  157.08 

22  =  158.10  -  (0.4  X  0.8)  +  .000005  X  40^  =  157.89 

C.  Station 

22+  40, elev.  3=  152.50  +  (7  X  0.8)  =  158.10 

In  special  cases  it  may  be  more  convenient  to  note  that  at 
one-quarter  of  the  distance  from  A  to  B  the  correction  is  ^^  of 
eh,  at  one-half  the  distance  it  is  J  of  eh  and  at  three-fourths  of 
the  distance  it  is  y^g-  of  eh. 

CONSTRUCTION— EARTHWORK, 

48.  Slopes  and  Cross-sections.  The  construction  of  a  road- 
bed  of  sufficient  width  which  is  level  or  nearly  so,  implies  in  gen- 
eral cuts  and  fills  of  various  depths.     An  essential  feature  of  the 


50 


RAILROAD  ENGINEERING 


work  is  that  the  slopes  shall  be  such  that  the  banks  shall  not  give 
way  and  disintegrate,  filling  up  the  the  cuts  and  narrowing  the 
tops  of  the  fills.  The  rate  of  slope  is  always  indicated  by  a  ratio 
of  which  the  first  number  indicates  the  horizontal  distance  and  the 

second  the  vertical.  Frequently 
the  second  number  is  made  uni- 
formly one  and  then  the  first  may 
be  a  fraction  or  a  compound  num- 
ber. The  following  slope  ratios 
will  be  so  indicated.  The  rate  of 
slope  is  variable,  depending  on  the 
kind  of  soil.  When  a  rock  cut  is 
very  hard  and  firm,  a  vertical  slope 
may  be  used,  although  on  account 
of  seams  in  the  rock  which  make 
slipping  possible  after  the  rock  has  begun  to  disintegrate,  the  rock 
is  generally  taken  out  until  the  slope  will  average  more  nearly  one- 
fourth  horizontal  to  one  vertical.  As  the  character  of  the  material 
changes  from  rock  to  earth,  the  slope  ratio  for  cut  must  be  flattened 
until  for  good,  firm,  loamy  soil  a  slope  of  1 : 1  is  proper.  When  first 
excavated  earth  will  stand  at  a  much  steeper  slope  than  this,  but  the 


Fig.  80. 


Fig.  31. 

first  hard  rainstorm  will  start  the  disintegration, which  will  proceed 
until  the  3lope  becomes  about  1: 1.  And  as  it  is  generally  cheaper 
to  make  the  required  excavation  during  the  original  construction, 
the  proper  slopes  should  be  made  then.  Some  kinds  of  earthy 
soil,  such  as  quicksand,  require  even  flatter  slopes.  Cases  have 
been  known  where  a  cut  has  not  ceased  to  slip  until  it  had  assumed 
a  slope  of  about  4: 1.    The  proper  slope  for  a  fill  composed  of  loose 


RAILROAD  ENGINEERING  51 

rock,  as  it  is  blasted  from  an  excavation,  is  about  1:1,  but  when 

the  side  hill  is  so  steep  that  the  slope  would  be  very  long,  a  much 

sleeper  slope  may  be  tolerated  if  some  care  ie  taken  to  form  the 

stones  of  the  fill  into  a  rough  dry  wall.     A  fill  of  earth  usually 

requires  a  slope  of  1.5  :  1.     If   the   material   of   which  the  fill  is 

made  is  exceptionally  soft, 

such  as  would  require  a 

very  fiat  slope  in  cut,  then 

a  correspondingly  flatter 

slope  should  be  made  with  '''^nnflltfVii'itnfi^iuT 

the  fills,   but  in   such  a  Pig,  32. 

case  it  is  quite   possible 

that  it  would   be  preferable  to  "waste"  such  treacherous  soil  and 

make  the  fill  of  more  suitable  soil,  even  if  it  had  to  be  "borrowed." 

The  following  illustrations  will  show  some  typical  cross -sections 

in  various  kinds  of  soil. 

49.  Width  of  Roadbed.  A  mistaken  effort  at  economy 
will  often  be  the  excuse  for  cutting  down  the  width  of  roadbed  to 
such  an  amount  that  there  is  no  room  for  adequate  ditches  in  cuts, 
and  the  deterioration  of  the  track  due  to  lack  of  drainage  is  a  very 
serious  quantity.  Even  fills  are  sometimes  made  so  narrow  that 
the  inevitable  washing  due  to  occasional  heavy  rains  will  endanger 
the  stability  of  the  track.  A  study  of  the  standard  roadbed  cross- 
sections  adopted  by  the 
principal  railroads  of  the 
country  shows  that  the 
average  width  for  an 
earthwork  cut  for  single 

p.     g^  track  is  about  25  feet. 

This  includes  about  four 
or  five  feet  on  each  side  for  a  ditch.  For  double  track  this  width 
is  increased  by  about  13  feet,  the  usual  width  between  track  centers 
for  two  tracks.  The  average  width  for  the  top  of  a  single  track 
fill  is  a  little  over  17  feet.  Sixteen  feet  is  about  the  minimum 
for  good  construction. 

50.  Constructive  Details—Ditches.  A  well-known  railroad 
engineer  used  to  say  that  ditches  were  more  important  than  ballast. 
A  lack  of  good  ditching  will  ruin  a  roadbed  in  spite  of  the  best 

61 


52 


RAILROAD  ENGINEERING 


ballast,  while  a  comparatively  small  expenditure  in  ditching  will 
largely  compensate  on  a  cheap  road  for  the  lack  of  good  ballast. 
The  bottom  of  the  ditch  should  be  from  one  to  two  feet  below  the 
bottom  of  the  ties.  The  slope  of  the  sides  should  not  be  steeper 
than  1:1  unless  in  solid  rock.     The  bottom  should  be  one  to  two 


Fig.  34 


feet  wide.  Sometimes  they  are  made  V-shaped,  but  that  shape  is 
hydraulically  bad  and  the  bottom  quickly  fills  up.  Suh-grade. 
The  upper  surface  of  the  earthwork,  commonly  called  sub-grade, 
is  usually  made  a  level  plane,  but  it  is  preferable  to  make  two 
sloping  planes  having  a  crown  at  the  center  of  about  six  inches. 
Rolling  the  sub-grade  with  a  road  roller  before  placing  the  ballast 
has  been  specified  by  the  N.  Y.  Central  R.R.  When  this  is  done, 
the  water  that  runs  through  the  ballast  will  more  readily  run  off 
to  the  side  ditches  instead  of  soaking  into  the  sub-soil.  If  the 
vegetable  mould,  which  is  usually  found  on  the  surface  and  which 
is  the  first  of  the  excavation 
for  cuts,  is  laid  on  one^side 
instead  of  being  placed  at 
the  bottom  of  the  nearest  fill 
and  is  afterward  spread  on 
the  faces  of  the  slopes  of  the 
cuts  and  fills,  a  growth  of 
vegetation  will  quickly  start 
up  which  will  save  the  slopes  from  the  effects  of  rain  washing  and 
will  quickly  repay  the  slight  additional  expense.  Even  an  imme- 
diate sodding  of  the  slopes  during  construction,  although  it  will 
add  considerably  to  the  original  cost,  will  usually  save  much  more 


Fig.  35. 


RAILROAD  ENGINEERING  53 

than   its   cost  by  a  reduction  of  maintenance  charges  during  the 
iirst  few  years. 

EARTHWORK— SURVEYS. 

51,  Nature  of  the  Problem.  The  mass  of  earthwork  which 
is  removed  has  an  exceedingly  irregular  form.  The  surveys  have 
the  double  object  of  staking  out  the  limits  of  the  earth  to  be 
removed  and  placed  elsewhere  and  also  of  computing  the  volume 
of  that  earthwork.  The  computation  of  any  volume  means  the 
computation  of  some  geometrical  form  or  combination  of  forms 
which  are  assumed  to  represent  with  sufficient  accuracy  the  actual 
volume  under  consideration.  If  an  approximate  result  is  suffi- 
ciently close,  some  simple  geometrical  form,  easily  measured  and 
easily  computed,  will  be  selected  as  representing  the  volume.  But 
as  greater  accuracy  is  required,  the  more  complicated  must  be  the 
form.  Some  of  the  faces  of  the  volume  are  simple  and  determin- 
ate. Sections  are  usually  taken  100  feet  apart  and  perhaps  closer 
if  the  ground  is  very  irregular.  Such  sections  are  plane  surfaces. 
The  side  slopes  are  also  plane  surfaces.  But  the  side  representing 
the  surface  of  the  earth  is  actually  rough  and  irregular;  usually 
it  is  too  irregular  to  be  considered  a  plane  even  approximately. 
The  surface  line  of  each  end  section  is  considered  as  a  broken  line 
of  one  or  more  parts,  and  it  is  generally  assumed  that  plane  or 
w^arped  surfaces  connecting  corresponding  lines  in  the  end  sec- 
tions will  lie  sufficiently  close  to  the  actual  surface  so  that  the 
error  involved  will  be  wnthin  the  desired  limits.  It  may  thus  be 
seen  that  the  accuracy  of  the  computation  depends  not  only  on  the 
accuracy  of  the  mere  numerical  work  but  even  more  on  the  judg- 
ment used  by  the  surveyor  in  so  selecting  the  places  for  the  cross- 
sections  and  the  points  of  any  cross-section  that  the  geometrical 
form  assumed  to  represent  the  volume  shall  agree  with  the  actual 
volume  of  earth  as  closely  as  desired.  The  survey  therefore  con- 
sists first  in  determining  at  each  section  the  points  where  the  side 
slopes  intersect  the  surface  and  then  the  elevation  and  distance 
from  the  center  of  points  so  chosen  that  straight  lines  joining 
these  points  will  lie  very  nearly  in  the  surface  of  the  ground. 

52.  Position  of  Slope  Stakes.  The  slope  stakes  are  set 
where  the  side  slopes  intersect  the  surface.     As  seen  by  the  fig- 


54 


RAILROAD  ENGINEERING 


lire,  these  intersections  depend  on  the  elevation  of  the  roadbed, 
which  in  turn  depends  on  the  depth  of  cut  or  fill.  In  Fig.  36  it 
may  readily  be  seen  that 

1 
2 
1 


Fig.  36. 

in  which  .v  is  the  slope  ratio  of  the  side  slopes,  horizontal  to  verti- 
cal.    See  §48. 
Similarly  it  is  seen  in  Fig.  37  that 


«^i  =  9  ^>  ^  ^*^'  ('^ "  yO 


x^=^h  -f    s{il  +  yj 


(38) 


But  in  each  of  these  equations,  both  x  and  y  are  unknown  quanti- 
ties, and  it  is  impracticable  to  depend  on  a  strictly  mathematical 
solution.  The  simplest  method  is  to  find  by  trial  the  location  of 
points  which  will  satisfy  the  equations.     An  experienced  man  will 


64 


RAILROAD  ENGINEERING  55 

sometimes  determine  such  a  point  in  a  single  trial  and  generally 
the  second  trial  will  be  sufficient.     As  a  first  approximation,  we 

may  note  that  a  is  at  such  a  position  that  its  x  is  ac  =  -^  J  +  sd. 

The  added  distance  out  to  iti  equals  the  added  drop  times  s.  As- 
sume that  in  Fig.  36,  d  =  7.7,  J  =  20  and  s  =  l.b  :  1.  The  dis- 
tance ae  r=  10  -f  (1.5  X  7.7)  =  21.55.  But  experience  will 
suggest  that  the  required  point  i/i  is  about  8  feet  lower  down  and 
therefore  about  (1.5"  X  8)  or  12  feet  further  out.  As  a  first  trial 
with  the  rod,  the  rod  is  placed  at  n',  34  feet  out  (21.55  +  about 
12),  where  a  rod  reading  of  b  (=  10.6)  is  found.  Subtracting 
k  (^=  3.5)  we  have  7.1,  the  ''?/"  of  that  point.  Substituting  this 
value  of  y  in  the  first  part  of  equation  37,  we  compute  Xi  to  be 
32.2.  This  is  the  point  n  in  Fig.  36,  at  a  distance  x"  (which  is 
less  than  x)  from  the  center.  This  shows  that  even  32.2  is  too 
far  out.  Another  trial  is  made  at  30.2  feet,  where  the  rod  reading 
is  found  to  be  9.3,  which  means  that  the  y  is  9.3  —  3,5  =  5.8, 
which  substituted  in  the  equation  gives  x  =  30.25.  This  checks  so 
closely  with  30.2,  that  it  may  be  considered  satisfactory.  On 
rough  ground  it  is  an  utterly  useless  refinement  to  attempt  to  do 
work  closer  than  the  nearest  tenth  of  a  foot,  for  the  almost  un- 
avoidable  inaccuracies  will  often  have  a  greater  effect  than  a  change 
of  even  a  tenth  in  such  work.  The  above  explanation  is  given 
in  detail  so  as  to  show  the  method.  Some  such  method  is  neces- 
sary for  the  inexperienced  man,  but  even  a  short  experience  will 
enable  a  man  to  estimate  the  correction  to  his  first  trial  very 
quickly  and  surely  so  that  the  second  trial  will  be  satisfactory,  and 
without  a  detailed  solution  as  above  of  all  the  work. 

In  Figs.  36  and  37,  the  ground  has  been  shown  as  having  a 
practically  uniform  slope.  The  determination  of  the  slope  stake 
is  not  affected  essentially  by  the  nature  of  the  ground  between  the 
center  and  the  slope  stakes.  In  Fig.  42  is  shown  a  more  compli- 
cated cross-section  in  which  the  elevation  of  each  intermediate 
point  above  the  roadbed  and  its  distance  from  the  center  must  be 
measured.  These  are  determined  by  setting  up  the  level  so  that 
it  is  higher  than  any  point  in  the  cross-section  and  noting  its 
height  above  the  stake  at  the  center.  This  rod  reading  added  to 
the  given  center  cut  d  gives  the  height  of  the  instrument  above 


,56  RAILROAD  ENGINEERING 

the  roadbed.  This  is  called  the  H.I.  Subtracting  the  rod  read- 
ing for  any  point  from  the  ILL  gives  the  height  of  that  point 
above  the  roadbed.  In  the  case  of  a  fill,  which  may  be  illustrated 
by  turning  Fig.  42  upside  down,  the  level  may  be  either  above  or 
below  the  roadbed.  This  modifies  the  above  rule  somewhat,  but 
the  same  principle  applies — determine  the  difference  of  elevation 
of  each  point  of  the  surface  of  the  ground  and  the  roadbed, 

COMPUTING  THE  VOLUME. 

53.  Common  Methods.  Sometimes  an  approximate  com- 
putation of  the  volume  of  the  earthwork  is  made  from  the  work 
of  the  preliminary  survey,  so  as  to  get  an  approximate  idea  of  the 
amount  of  earthwork  on  a  route,  and  therefore  its  cost.  To  do 
this,  a  more  or  less  approximate  measure  of  each  cross-section  is 
taken  and  then  the  distance  between  any  two  cross-sections  is 
multiplied  by  the  half-sum  of  the  two  areas.  The  sum  of  all  such 
products  gives  the  total  volume.  Such  a  method  is  mathematically 
inaccurate,  but  the  approximation  in  the  cross-sectional  areas,  and 
some  other  reasons,  will  probably  introduce  still  further  inac- 
curacies. These  various  methods  will  be  described  in  the  order  of 
increasing  accuracy. 

54.  Level  Sections.  From  Fig.  38  may  readily  be  derived 
the  equation 

Area  =  {a  -^  ^^A'  --y  (39) 

If  Aq  is  the  area  of  the  initial  section  and  Aj,  Ag,     •     •     A^  be  the 

areas  of  the  succeeding  and  final 
sections,  which   are  at  a  uniform 


^/^//m/^Ammw/m/^'/    distance  apart  of  1,  then  the  total 
I-  -[-  -i-i  -H  yffi^  volume  will  be 

wfdmjw 

?--Y-'  Volume  =  i-  qA„  +  2  (A,  +  A, 

^'^■''-     .'  +  ••  +A,.,)  +  AJ     (40) 

Of  course  I  is  usually  100.     The  ^—  for  each  section  is  a  constant, 
and  therefore  the  subtractive  term  issimply  this  constant  multi- 


RAILROAD  ENGINEERING 


67 


plied  by  the  number  of  times  the  areas  are  used  in  the  summation. 

Example.     Given  the  center  heights  set  down  in  the  second 

column  of  the  tabular  form.     Width  of  roadbed,  20  feet;  slope, 

1.5  :  1.    Then  d  =  6.7.    The  remainder  of  the  solution  is  evident. 


Sta. 

Center 
Height. 

(a  +  d) 

(a  +  d)2 

(a-fd)2s      ^ 

42 
43 
44 
45 
46 

1.4 

2.6 
4.3 
8.9 
3.1 

8.1 

9.3 

11.0 

15.6 

9.8 

65.61 

86.49 

121.00 

243.36 

96.04 

98.41 
129.731 
181.50 
365.04  J 
144.06 

X 

98.41 

r 259. 46 

2  =       363.00 

1  730.08 

144.06 

ah 


6.7  X  20 


=  67 


1595.01 
'8  X  67     =536. 

io5^:oi 


1059  X  100 

~T">r2T~ 


1961  cubic  yards. 


The  above  method  invariably  gives  results  which  are  some- 
what too  high,  for  the  volume  between  two  "level  sections  "  is  less 
than  the  length  times  the  mean  of  the  areas.  When  the  areas  are 
equal,  the  error  is  zero,  but  it.  increases  as  the  square  of  the  differ- 
ence of  the  center  cuts,  or  fills.  But  since  sections  are  almost 
never  truly  level,  the  assumption  that  they  are  level  will  usually 
introduce  an  error  largely  in  excess  of  the  theoretical  error.  Some- 
times the  above  method  is  used,  aided  perhaps  by  tables,  by  taking 
center  cuts,  or  fills,  from  a  profile  and  assuming  that  the  actual 
volume  will  be  the  equivalent  of  the  volume  computed  as  above.* 
Such  a  method  has  its  value  as  a  mean^  of  comparing  two  routes, 
but  the  error  is  apt  to  be  very  great. 

55.  Equivalent  Sections.  The  following  method  is  some- 
times used  when  the  cross -sections  are  irregular  and  especially 
when  there  is  disinclination  or  inability  to  use  a  more  accurate 
method.  Each  cross-section  is  plotted  on  cross-section  paper. 
Then  a  thread  (mn)  is  so  laid  that  (by  estimation)  it  equalizes  the 
spaces  al)ove  and  below  it  (see  Fig.  39).  The  distances  out  from 
the  center  of  the  intersections  of  this  mean  line  wnth  the  side  slopes 
are  scaled  from  the  drawing  and  are  here  called  £»i  and  x^.  Since 
s  is  the  slope  ratio,  s  =  Xi  -t-  mo  =  x^  ^^  nj).     Then  the  required 


58 


RAILROAD  ENGINEERING 


area  equals  the  area  mnop  minus  the  triangles  mso^  njjs,  and  the 
"  grade  triangle,"  which  means  that 


1  / 

'a;i+.rr 

)(. 

r)    - 

■t"l 

Xi 

av 

Xr 

ah 

TT  1 

i+.i 

+ 

2   V 

.      s     > 

/ 

S 

2 

s 

2 

2 

.ri  av 

ah 

(^ 

s 

2 

^.w 


Area 


Note  the  simplicity  of  the 
form.  When  *^  =  1:1,  the 
area  equals  the  mere  product 
of  these  two  side  distances 
minus  the  constant  correc- 
tion-^<7J.    The  areas  being 

computed,  the  volumes  are 
obtained  exactly  as  in  equa- 
Fig.  39.  tion  40.     As  in  the  previous 

section,  it  may  readily  be 
shown  that  the  method  of  averaging  end  areas  does  not  give  correct 
results  except  in  the  special  case  when  the  distances  to  the  right 
(or  to  the  left)  at  adjacent  stations  are  equal,  and  when  these  dis- 
tances are  nearly  equal  the  error  is  small.  As  an  approximate 
method,  it  is  very  rapid  and  good.  As  before,  the  correction  is 
usually  negative,,  i.e.,  the  computed  volume  is  too  large. 

56.  Volume  of  a  Prismoid. 
Fig.  40  represents  in  a  perspective 
view  a  prismoid,  formed  between 
two  triangles  which  lie  in  parallel 
planes.  The  surfaces  which  join 
the  corresponding  sides  of  the  tri- 
angles are,  in  general,  warped  sur- 
faces. It  may  be  proved  that  the  1'^^-  ^^• 
volume  of  such  a  prismoid  equals 

one-sixth  of  the  perpendicular  distance  betw^een  the  parallel  planes 
times  the  sum  of  the  two  eiid  triangles  and  four  times  the  middle 
triangle  (cut  by  a  plane  parallel  to  the  end  planes  and  midway 
betw^een  them).     This  may  be  stated  algebraically  as  follows: 


RAILROAD  ENGINEERING  59 

Volume  =  !^^  /A,  +  4A^  +  A  A         (42) 

It  may  also  be  proved  that  the  foririula  holds  good  regardless  of  the 
values,  relative  or  absolute,  of  ?>i,  ^.^,  h^  or  h.^.  Therefore  it  holds 
good  when  h^  =  O,  and  the  prismoid  becomes  a  wedge.  It  also 
holds  good  when  both  h^  and  h^  become  zero  and  the  prismoid,  becomes 
a  pyramid.  But  since  the  formula  holds  good  for  all  these  forms 
individually  it  holds  good  for  them  collectively,  and  since  any 
prismoid,  having  bases  of  straight  lines  lying  in  parallel  planes 
and  with  plane  or  warped  surfaces  connecting  those  ends,  can  be 
considered  as  made  up  of  a  collection  of  triangular  prismoids, 
pyramids  and  wedges,  the  formula  evidently  holds  for  such  a 
prismoid. 

If,  in  equation  42,  A^  were  the  mean  of  A^  and  A2,  then  we 
could  obtain  the  true  volume  by  averaging  end  areas.  Some  of 
the  exceptional  cases  where  this  is  true  have  already  been  men- 
tioned.  In  general  it  is  a  complicated  and  impracticable  problem 
to  compute  the  area  of  the  middle  section.  But  it  is  quite  possi- 
l)le  to  compute  the  correction  which  must  be  applied  to  the  result 
found  by  averaging  end  areas,  and  these  methods  w411  be  used  in 
the  following  more  accurate  solutions.  Applying  equation  42  to 
Fig.  40,  we  have 

Volume  =^^l2  h  h  +  ^  V  2  ^T'  "^T^/  +  2  ^-'  ^  J 
But  the  approximate  volume,  computed  by  averaging  end  areas,  is 

Appr.  vol.  =-^(-y^»,  li,  +  -^  ^7^2) 

Subtracting  tlie  approximate  volume  from  the  true  volume,  we 
obtain  the 

Correction  =  „  \{h^  -  b.^)  [h^  -  h^)\         (43) 

57.  Three=Level  Sections.  When  the  ground  is  fairly  uni- 
form so  that  it  may  be  said  without  great  inaccuracy  that  it  slopes 
uniformly  from  the  center  to  each  slope  stake,  then  the  volume 
may  be  computed  from  the  positions  of  these  three  points  and  the 
sections  are  called   "three-level   sections."       The  area  of  such  a 


GO 


RAILROAD  ENGINEERING 


section  =  ~^(^^  +  ^^) '^^ — ^ab.  If  we  consider  two  such  adja- 
cent sections  and  compute  the  volume  by  the  method  of  averaging 
end  areas,  we  will  obtain  as  the  volume 

Vol.  =  -4-L('^  +  ^^')  f'''  -  ''^'  +  (^''  +  ^n  ^^^"  -  ^^'^^J 

Dividing  by  27  to  reduce  immediately  to  cubic  yards,  we  have 
when  I  =  100, 

25  25  25  25 

Vol.   =  ^  (v^  +  d')  w  -^ab  +  -^  {a  +  (7")  w'* --^ctt>    (44) 

When  it  is  desired  to  make  the  computation   still  more  accurate, 

the  prismoidal  correction  may  be  computed  as  follows.     We  may 

compute  separately  the  pris- 
moidal correction  for  each  of 
the  two  triangular  prismoids. 
These  two  prismoids  together 
include  the  triangular  "  grade 
prismoid"  under  the  road- 
bed, but  since  there  is  no  pris- 
moidal correction  to  the  grade 
prismoid,  such  correction  as 
may  be  computed  applies 
solely  to  the  volume  actually 

excavated.     Applying  equation  43  to  the  dimensions  in  Fig.  41,  we 

have  for  the  left  side 

Pris.  Corr.  -=  p-  [(^  +  d')  -  (^  +  ^/")]  (^''i"  -  '^"lO.  which 

reduces  to  =  j-r  (^d'  -  d")  (^w{'  -  w{) 
For  the  right  side,  we  may  compute  similarly 
Pris.  Corr.  =  ^  {d'  -  d")  (w^"  -  <) 
For  the  two  triangles  we  have 
Pris.  Corr.  =.  —  (^'  _  f7")[(7^?r  +  w^")  -  {w{  +  Oj 


RAILROAD  ENGINEERING 


61 


Making  I  =  100  and  dividing  by  27  to  reduce  to  cubic  yards  we  have 

OK 

Pris.  Corr.  =  -^  {d'  -  d")  {w"  -  lo)        (45) 


An  inspection  of  equation  45  will  show  that  if  either  the  center 
cuts  or  the  total  widths  at  two  adjacent  sections  are  equal  or  nearly 
so,  the  prismoidal  correction  is  zero  or  is  so  small  that  it  may  be 
neglected.  This  frequently  enables  one  to  decide  that  the  pris- 
moidal correction  will  evidently  be  so  small  that  it  will  be  useless 
to  compute  its  exact  value.  It  usually  happens  that  when  d'  >  d'\ 
in  is  also  greater  than  w".  This  means  that  the  correction  com- 
puted from  equation  45  will  usually  be  negative^  which  means 
that  for  three-level  sections  the  results  computed  by  averaging  end 
areas  will  usually  be  too  large. 

A  very  great  economy  of  time  and  accuracy  result  from  tabu- 
lating all  the  computations  in  earthwork.  Such  work  can  be 
readily  reviewed  to  check  it  or  to  discover  a  supposed  error.  An 
illustration  of  such  a  solution  is  given  below. 

58.     Numerical  Example. 


Sta. 

Center. 

Left. 

Right. 

a  +  d 

w 

Yards. 

52 
53 
54 

+  65 
55 

3.1C 

6.7C 

10.6  C 

15.5  C 

8.7C 

9.6C 

1.2  C 

11.1 
14.7 
18.6 
23.5 
16.7 

40.2 
47.4 
59.1 
68.4 
51.3 

413 

645 

1018 

1488 

793 

702 
1307 
1397 

674 

26.4 
11. 4C 

13.8 
4.2C 

29.1 
15.6  C 

18.3 

7.8C 

35.4 
19.0  C 

23.7 
10.6  C 

40.5 
12.4  C 

27.9 
5. 80 

30.6 

20.7 

d'  -  d' 


3.6  i-f  7.2 

3.9   +11.7 
4.9  1+  9.3 


+6.8 


17.1 


Pris. 
corr. 


I 

-  8 
-14 

-  9 
-13 


Roadbed  24'  wide  in  cut.      Approx.  vol.  =  4080 
Slope  1.5  :  1.  Pris.  corr.  =  —44 

h 


-44 


i-^=«-» 


True  vol.    =  4041 


•^o 


ah  =  178 


9.6C  . 


In  the  above  form,  -^ — -  in  the  third  column  means  that  the  slope 
stake  on  the  left  side  of  Sta.  52  is  9.6  feet  above  the  elevation  of 


02  RAILROAD  ENGINEERING 

the  roadbed  which  is  here  in  cmt  C;  also  that  it  is  20.4  feet  out 
from  the  center.  This  notation  is  also  used  to  indicate  the  posi- 
tion of  "intermediate  points,"  the  numerator  of  the  fraction  giv- 
ing the  depth  of  cut  or  fill  (C  or  F)  and  the  denominator  the 
distance  from  the  center.  The  other  points  in  the  third  and  fourth 
columns  are  to  be  interpreted  similarly.  Column  5  is  found  by 
adding  a  (^=8.0)  to  column  2;  '^^  in  each  case  is  the  sum  of  the 
two  denominators  in  the  same  horizontal  line;  413  (in  column  6) 

25 
=^97     X  11.1  X  40.2.     A  short  method  of  performing  this  mul- 
tiplication   will    be    given   later.      The   solution   of    equation   44 
applied  to  this  case  is: 

Vol.  =  413  -  178  +  045  -  178  =  702. 

Similarly     1397  --  ~^^  (1018  -  178  +  1488  -  178). 

and       074  =  ^~  (1488  -  178  +  703  -  178). 

-  3.0  =  3.1  -  0.7     and    -f  7.2  =-  47.4  ~  40.2.       -  8  =  ?5 

81 

(-  3.6)  X  (  +  7.2) ;  see  equation  45.  Note  that  in  this  case  the 
prismodial  correction  is  about  1  per  cent  of  the  total  volume. 
The  errors  due  to  inaccurate  cross-sectioning  will  frequently  be 
more  than  this.  The  volume  4036  cubic  yards  is  the  'precise  vol- 
ume (barring  the  neglect  of  the  fraction  of  a  yard)  of  the  prismoids 
given  by  the  notes.  Whether  these  prismoids  actually  represent 
the  true  volume  of  the  earthwork  depends  entirely  on  the  cross- 
sectioning  and  is  entirely  out  of  the  hands  of  the  computer. 

25 
59.     Computation  of  Products.     The  products  ^^<2  J  maybe 

written   j-t^.     These  products  are  always  the  combination  of  two 

variable  terms  and  a  constant.  It  thus  becomes  possible  to  con- 
struct tables  which  will  give  these  products  for  any  given  height 
and  width.  CrandalPs  Earthwork  Tables  are  computed  on  this 
basis.  But  these  products  are  also  obtained  with  great  ease  by 
means  of  a  slide  rule,  provided  it  is  large  enough  to  give  the 
required  accuracy.  The  108  mark,  being  so  constantly  in  use 
should  have  a  special. mark  so  that  it  may  be  found  without  effort. 


RAILROAD  ENGINEERING  63 

As  a  numerical  illustration,  take  the  first  of  the  above  cases.     Set 

the   108   mark   of  the  upper  scale  on  the  111  mark  on  the  lower 

scale.     Then   look  for   the   402  mark  on  the  upper  scale  and  note 

that  it  is  nearfy  over  the  413  mark  on  the  lower  scale.     "While  it 

is  possible   to  devise  set  rules   to  determine  the  position  of  the 

decimal  point,  it  is  considered  that  a  hasty  mental  solution  of  the 

problem   will  decide   the   point   quicker  and  w4th   less  chance  of 

error.     For  example — the  product  of  the  two  variable  quantities 

is  always  divided  by  1.08,  which  means  that  the  final  result  will  be 

a  little  less  than  the  simple  product  of  the  two  variables,  11  X  40 

=  440.     Therefore  413  is  evidently  the  correct  result,  rather  than 

25 
41.3  or  4130.     The  products  — -  xy  are  similarly  obtained  since 

25  1 

81  ^^  ^^'  ^^^  ^^  ^^^  mark  can  be  used  instead  of  the  108.   For 

example,  the  slide  rule  shows  that  ^^ q  9  / '- —  =  -  8  to  the 

nearest  cubic  yard.  As  to  the  decimal  point — 3.6  -^  3.24  is 
something  more  than  one;  therefore,  the  result  is  something  more 
than  7.2.  Therefore  it  is  8,  rather  than  80  or  0.8.  If  the  student 
has  neither  tables  nor  slide  rule,  the  multiplication  of  the  two 
variables  (in  columns  5  and  6)  and  the  division  of  the  products  by 
the  constant  1.08,  may  be  made  so  mechanical  and  systematic  that 
it  may  be  done  quickly  and  accurately  although  it  is  much  slow^er 
than  the  slide  rule  method. 

60.  Irregular  Sections.  The  distance  from  the  center  and 
the  height  above  or  below  the  roadbed  must  be  obtained  for  each 
break  in  the  surface  between  the  slope  stakes.  Then,  in  Fig.  42, 
by  dropping  perpendiculars  from  each  point  to  the  roadbed  line, 
the  total  area  is  divided  into  a  number  of  trapezoids,  the  sum  of 
the  areas  of  which  (less  the  areas  of  the  two  triangles  under  the 
side  slopes)  equals  the  total  area  of  the  section.  For  Fig.  42,  the 
area  would  be  stated  algebraically  as  follow^s: 

Area  =  \{r  +  *■)  {f-g)  +  \-  (.v  +  t)    (j/  -  A)  +  ^^(t+  d)h 
+  y  {d  +  '0)j  +  -3-  (y  +  w)  {k  -j)  -  —  w{l---^  h) 


64 


RAILROAD  ENGINEERING 


Expanding  this  and  collecting  terms,  of  whicli  many  will  cancel 
out,  we  Lave 

Area  =  -2^[_/*'  +  ^  (^  -  ''')  +  J(^i(l-  ^)  +  ^o  +i  {d -  w)  +  -g-  ^ 


{r  +  ^)]. 


(46) 


Although  the  above  equation  looks  as  if  it  applied  only  to  the  par- 
ticular  case  given,  yet  a  little  study  of  it  will  show  that  the  terms 
follow  a  law  so  general  that  the  reduced  equation  for  the  area  of 
any  section,  no  matter  how  complicated  or  how  many  points  it 
may  have,  may  be  written  out  by  a  literal  obedience  of  the  follow- 
ing rule: 

Area  equals  one-lialf  the  sum  of  products  ohto/med  as  follows : 


Fig.  42. 

The  distance  to  each  slope  stake  times  the  height  above  grade 
of  the  point  next  inside  the  slope  stake; 

The  distance  to  each  interTuediate  point  in  tarn  tunes  the 
height  of  the  point  just  inside  tninus  the  height  of  the  point  just 
outside; 

Finally^  one -half  the  width  of  the  roadbed  times  the  sum  <f 
the  slope  stake  heights. 

The  above  rule  may  be  followed  literally  whether  there  are 
forty  intermediate  points  or  one,  or  even  ^ume.  When  there  are 
no  intermediate  points  the  terms  for  that  side  reduce  to  one — the 
distance  to  the  slope  stake  times  the  height  of  the  point  next  inside 
(which  in  this  case  is  the  center).  For  three-level  ground  (see 
Fig.  41),  we  would  have  three  terms; 


RAILROAD  ENGINEERING  65 

Area  ^=  w^d  -\-  u\  d  ^  -;r  ^  (^'i  "•"  ^'r)'  ^'l^i^h  reduces  to  two  terms 

Area  =  wd  -\-  -^h  {Ji\  +  Ar)- 

The  method  of  §  57  has  the  advantage  that  one  of  the  two 
terms  for  each  section  is  constant  for  all  sections — in  the  numerical 
case  of  §  58  it  is  178  cubic  yards.  By  the  above  method  the  two 
terms  for  each  section  are  variable.  Nevertheless,  when  the  cross 
sections  usually  have  one  or  more  intermediate  points  and  there- 
fore the  method  of  §  60  must  be  used,  and  an  occasional  section  is 
found  with  no  intermediate  points,  it  is  better  for  the  sake  of  uni- 
formity to  apply  the  above  method  rigidly  and  thereby  avoid  the 
possible  confusion  and  error  that  would  result  by  the  use  of  another 
method.  Probably  no  time  would  be  saved  by  the  change  of 
method. 

61.  Prismoidal  Correction.  The  above  method  of  irregular 
sections  is  capable  of  being  followed  to  its  logical  conclusion,  and 
a  computation  for  volume  made  which  is  mathematically  correct, 
provided  that  it  is  noted  on  the  ground  how  the  points  of  adjacent 
sections  are  joined,  so  that  the  warped  surfaces  thereby  developed 
shall  lie  as  closely  as  possible  in  the  actual  surface  of  the  ground. 
But  the  very  fact  that  the  cross-section  is  irregular  implies  that 
any  longitudinal  section  wnll  be  correspondingly  irregular,  and  this 
leads  to  the  suspicion  that  a  refinement  in  the  computations  may 
be  overshadowed  by  a  much  larger  but  unknown  difference  between 
the  volume  of  the  assumed  geometrical  solid  and  the  actual  volume 
of  the  earthwork.  In  order  to  obtain  a  correction  which  is  easily 
computed  and  which  gives  a  result  which  is  probably  much  nearer 
the  truth  than  no  correction  at  all,  the  following  method  is  much 
used:  Consider  \h2Xf0r  the  purpose  of  the  correction  the  ground 
is  "  three-level  ground  "  and  use  equation  45.  Numerical  compu- 
tations of  volumes  by  both  methods  have  shown  that  the  difference 
is  small,  and  is  perhaps  smaller  than  the  probable  error  on  the 
entire  work.  This  method  will  he  used  in  the  following  numerical 
solution : 

62.  Numerical  Example.  Volume  of  Earthwork  In  irreg- 
ular Ground.  The  first  tabular  form  gives  a  desirable  form  of 
notes  for  recording  the  field  work.    Note  that  the  station  numbers 

75 


66 


RAILROAD  ENGINEERING 


Sta. 


47 
46 
4-  42 
45 
44 


center]  cut  or 


1.2  c 

4.3  c 
13.6  c 

9.2  c 
3.2  c 


Left. 


4.2  c 

16.4 

5.1  c 

6.2  c 

17.6 

8.5 

20.2  c 

15.7  c 

14.4  c 

40.3 

32.4 

16.8 

12.3  c 

12.7  c 

6.8  c 

28.5 

16.0 

6.4 

6.0  c 

3.5  c 

19.0 


8.3 


Right. 


0.8  c 

11.2 

2.1  c 

1.6  c 

3.4 

12.4 

12.5  c 

9.6  c 

10.2 

,24.4 

9.2  c 

7.8  c 

8.5 

21.7 

1.8  c 

12.7 


Roadbed  20  feet  wide  in  cut.    Slope  1.5  :  1. 

FORM  FOR  REDUCING  THE  ABOVE  FIELD  NOTES. 


Sta. 

Width. 

Height. 

Yards. 

Center 
height. 

Total 
width. 

d'  -  d" 

w"  -  wf 

Approx. 
pris. 
corr. 

19.0 

3.5 

62 

3.2 

31.7 

44 

8.3 
12.7 
10. 

-    2.8 
3.2 
7.8 

-    22 
38 
72 

• 

28.5 

12.7 

335 

9.2 

50.2 

-  6.0 

+18.5 

-    34 

16.0 

-    5.5 

-    81 

45 

6.4 

21.7 

8.5 

-    3.5 
9.2 
1.4 

-    21 

185 

11 

10. 

20.1 

186 

765 

40.3 

15.7 

585 

13.6 

64.7 

-  4.4 

+14.5 

-    20 

32.4 

-    5.8 

-  174 

+  42 

16.8 
24.4 
10.2 
10. 

-    2.1 

12.5 

4.0 

29.8 

-    33 

282 

38 

276 

667 

17.6 

6.2 

101 

4.3 

30.0 

+9.3 

-34.7 

-  100 

8.5 

-    0.8 

-      6 

46 

12.4 
3.4 
10. 

2.1 
2.7 
6.7 

24 

8 
62 

675 

16.4 

1.2 

18 

1.2 

27.6 

+3.1 

-  2.4 

-      2 

47 

11.2 
10. 

1.2 
5.0 

12 
46 

265 

Approx.  volume  =  2372 
**       pr.  corr.  =  -156 
Corrected  volume  =  2216  cubic  yards. 


-  156 


76 


RAILROAD  ENGINEERING  67 

run  up  the  page.  By  this  method  the  "  fractions  "  which  show 
the  height  and  distance  out  of  each  point  are  recorded  in  their 
approximate  relative  position  when  the  note  book  is  held  looking 
ahead  along  the  line. 

It  should  be  noted  in  this  case  that  the  prismoidal  correction 
is  a  large  percentage  of  the  total  volume.  In  the  case  of  a  pyra- 
mid, the  correction  is  one-third  of  the  nominal  volume,  which 
means  that  it  is  50  per  cent  of  the  true  volume.  The  foregoing 
numerical  case  gives  the  notes  for  an  embankment  crossing  a 
gully,  and  in  such  cases  especially  the  prismoidal  correction  is 
always  large  and  should  not  be  neglected. 

63.  Side-hill  Work.  A  road  frequently  runs  along  the 
slope  of  a  hill  so  that  it  is  necessary  to  have  both  cut  and  fill  in 
the  same  section.  The  profile  at  such  a  place  will  indicate  little 
or  no  earthwork,  but  if  the  natural  slope  is  steep  and  the  roadbed 
wide  the  amount  of  earthwork  may  be  considerable.  Although  it 
is  possible  to  apply  the  general  rule  of  §60  to  such  cases,  it  is 
usually  simpler  to  compute  the  area  in  each  case  independent  of 
the  rule,  especially  when  the  section  forms  a  mere  triangle.  The 
areas  of  cut  and  fill  must  be  calculated  independently.  When  a 
section  of  cut  or  fill  is  found  at  one  station  and  is  not  found  at 
the  next,  accuracy  requires  a  knowledge  of  the  place  where  the 
cut  or  fill  ''  runs  out ".  That  small  volume  must  then  be  consid- 
ered a  pyramid  with  a  given  base  and  height.  In  general  the  end 
of  every  cut  or  fill  implies  the  existence,  at  least  for  a  short  dis- 
tance, of  side-hill  work.  Although  the  volumes  are  usually  small, 
yet  since  they  are  frequently  of  pyramidal  form,  the  prismoidal 
correction  is  usually  a  large  percentage  of  the  volume  and  hence 
should  not  be  neglected.  The  rule  of  §61  can  generally  be 
applied. 

64.  Borrow  Pits.  This  name  is  applied  to  places  from 
which  earth  is  taken  to  make  an  embankment  when  there  is  insuf- 
ficient excavated  material  in  the  neighborhood  or  when  the  mate- 
rial is  unsuitable  for  embankments.  Such  volumes  must  be 
measured  up  and  paid  for  the  same  as  other  excavation.  Some- 
times the  form  of  the  excavation  is  literally  that  of  a  rectangular 
pit,  in  which  case  the  simple  product  of  the  three  dimensions 


68 


RAILROAD  ENGINEERING 


Fig.  43. 


gives  the  volume.  But  usually  it  is  required  to  slope  the  sides; 
sometimes  the  material  is  obtained  by  widening  a  cut,  as  in  Fig. 
44.  If  the  borrow  pit  is  very  large,  several  cross-sections  should 
be   taken   at   sufficiently  close   intervals.      If   the   prismoids   into 

which  the  total  volume  is 
divided  have  substantially 
equal  bases,  the  prismoid- 
al  correction  will  be  small 
and  may  be  neglected,  but 
if  the  forms  are  pyramidal 
the  correction  should  be 
computed  It  may  be- 
come necessary  to  consider 
the  total  volume  as  made 
up  of  triangular  prismoids  and  compute  the  prismoidal  correction 
for  each  one  separately. 

65.  Correction  for  Curvature.  The  volume  of  a  solid,  gen- 
erated by  revolving  a  plane  area  about  an  axis  lying  in  the  plane 
but  outside  of  the  area,  equals  the  product  of  the  given  area  times 
the  length  of  the  path  of  the  center  of  gravity  of  the  area.  When 
the  centers  of  gravity  of  the  cross-sections  lie  in  the  center  of  the 
road,  where  the  length  of  the  road  is  measured,  no  correction  is 
necessary.  If  all  the  cross-sections  were  the  same  and  therefore 
had  the  same  eccentricity,  the  total  volume  could  he  computed  by 
the  above  rule.  But.  in  general  both  the  areas  and  the  eccentrici- 
ties vary  from  point  to  point, 
and  then  a  theoretically  exact 
solution  would  be  impracticable 
for  ordinary  work  if  not  impos- 
sible. But  a  sufficiently  prac- 
tical rule  can  be  developed  as 
follows:  Assume  a  curved  pris- 
moid,  of  uniform  cross-sections 

and  therefore  of  uniform  eccentricity.  Call  that  eccentricity  e. 
Let  R  be  the  radius  of  the  center  line  of  the  road.  Then  the  length 
of  the  path  of  the  center  of  gravity  is  to  the  length  measured  on 
the  center  line  as  R  i  ^  :  R.     Therefore  we  have 

True  volume  :  nominal  volume  :  :  R  db  .^  :  R 


Fig.  44. 


RAILROAD  ENGINEERING  60 

Therefore  the  true  volume  of  the  prisnioid  —  ZA  — ^—,     "^^^^^ 

shows  that  the  effect  of  curvature  is  the  same  as  increasing  or 
diminishing  the  area  by  an  amount  which  depends  on  the  area  and 
the  eccentricity  and  that  the  increased  or  diminished  area  may  be 

found  by  multiplying  the  actual  area  by  the  ratio — =-^.      This 

being  independent  of  the  value  of  l,  it  is  true  for  infinitesimal 

lengths.    If  the  eccentricity  is  assumed  to  vary  uniformly  between 

two  sections,  the  equivalent  area  of  a  cross-section  located  midway 

ij  1      A      R  -f  *  (^'  -h  e")      m. 

between  the  two  end  areas  w^ould  be  Aj^ ~  '^    -.     inere- 

K 

fore  the  volume  of  a  solid   which,  when  straight,  would  be  -77-  ^ 

(A'  +  4A^  +  A")  would  then  become 
True  volume  = 

gi  [a'  (E  ±  .')  +  4A„  [R  ±\{e   +  e")]  +  A"  (R  +  .")] 

Subtracting  the  nominal  volume,  which  is  the  true  volume 
when  the  prismoid  is  straight,  we  have  the  correction  for  curva- 
ture as  follows 

Correction  =  4-— [^(A'  +  2A^)  e'  +  {2K^  +  A")  ^"J 

As  in  the  case  of  the  prismoidal  formula,  the  use  of  this 
equation  implies  a  knowledge  of  the  middle  area.  This  correction 
is  always  a  small  proportion  of  the  total  volume  and  is  frequently 
insignificant.  Therefore  no  appreciable  error  is  involved  in  mak- 
ing the  equation  read 

Curv.  corr.  =  -^  ( AV  +  A'V)  (47) 

66.  Eccentricity  of  the  Center  of  Gravity.  Thevahie  of"e". 
The  determination  of  the  center  of  g-ravity  of  a  complicated  irreg- 
ular cross-section  would  be  a  long  and  tedious  problem  and  is 
practically  unnecessary.  For  the  purpose  of  this  correction  it  is 
sufficiently  accurate  to  consider  all  sections  as  three-level  sections, 
except  in  side-hill  work,  where  they  should  usually  be  considered 
as  triangles.     In  Fig.  45,  the  eccentricity  of  the  center  of  gravity 


70 


RAILROAD  ENGINEERING 


of  the  whole  section,  including  the  grade  triangle,  may  be  com. 
puted  as  follows: 

[a  +  (I)  Xi  a?i     {a  +  d)  Xj.  x^ 
2"^        8~"         "2" 


e  = 


3         1  (a^i^-.V)        1 


{a  H-  d)  Xi      (a  -|-  d)  x^ 
2         +  2 


3  (^1  +  x^) 


(48) 


Substituting  this  value  of  e  in  equation  47,  we  have 

Curv.  corr.  =  g]g[A'  («^i'  -  <)  +  A"  «  -  x^")  ] 
But  the  approximate  volume  of  a  prismoid  may  be  written 


I 


Vol.  =  —  (A'  +  A")  =  _  A'  +  -^  A"  =  V  -f  Y" 

in  which  Y'  and  Y"  represent  the  number  of  cubic  yards  corre- 
sponding  to  the  area  at  each  station.  Substituting  these  values  in 
the  above  equation,  we  have 

Curv.  corr.  in  cu.  yd.  =  -g^  [y'  {x{  -  <)  +  Y"  {x{'  -  a?/')]  (49) 

The  value  of  ^,  found  in  equation  48,  is  the  eccentricity  of  the 
whole  area,  including  the  grade  triangle 
under  the  roadbed.  The  eccentricity  of 
the  true  area  is  greater  than  this  and 
equals 


Fig.  45. 


true  area  -\-  ^  ab 
true  p.rea 

The  required  quantity  (the  A'  e'  of  equa- 
tion 47)  equals  time  area  X  ^,  which 


equals  {true  area  +  -9-  (ib)  X  e.  The  value  of  e  (given  in  equa- 
tion 48)  is  a  remarkably  simple  term,  while  the  value  of  e^  is  very 
complicated  and  difficult  to  compute.  But  since  we  may  obtain  the 
true  corrective  value  by  using  e  and  at  the  same  time  adding  the 
yardage  corresponding  to  the  grade  triangle  to  the  yardage  cor- 
responding to  each  area,  it  is  best  to  do  it  in  this  way. 

For  any  one  curve  the  corrective  terms  are  all  divided  by  the 
quantity  3R.     If  tables  are  not  at  hand,  it  is  amply  accurate  to 


RAILROAD  ENGINEERING 


71 


compute  that  R 


5730 
"D" 


in  which  D  is  the  degree  of  the  curve. 


Even  equation  49  may  be  simplified  somewhat  in  actual  use.  The 
correction  at  each  station  has  the  form  — ^Wi5 — ~'     ^R  is  usually 

a  large  quantity;  for  a  4°  curve  it  is  4298.  [x^  -  x^.)  is  relatively 
very  small.  Their  ratio  times  V  is  never  a  very  large  quantity, 
and  it  is  frequently  less  than  unity,  when,  of  course,  it  should  be 
ignored.  An  approximate  solution  will  generally  show  that  the 
product  Y  [xi  -  Xj.)  is  roughly  twice  or  three  times  3R,  or  is  per- 
haps  less  than  one-half  3R,  and  then  the  corrective  term  for  that 
station  may  be  written  3,  2,  or  0  cubic  yards,  the  fraction  being 
ignored.  It  is  only  when  the  curvature  is  excessively  sharp  and 
the  eccentricity  very  great  that  the  curvature  correction  becomes  a 
large  percentage  of  the  volume. 

The  algebraic  sign  of  the  correction  is  most  surely  and  easily 
noted  from  a  consideration  of  the  direction  of  the  curvature  and 
on  which  side  the  earthwork  predominates.  If  the  center  of 
gravity  is  evidently  toward  the  inside  of  the  curve  the  true  vol- 
ume is  evidently  less  than  the  nominal  volume  and  the  correction 
should  be  negative.  When  the  curve  turns  to  the  right^  use  the 
form  (a?i  -  Xj.)\  when  it  turns  to  the  left,  use  the. form  (aj^  -  x^. 
The  algebraic  sign  of  the  correction  will  then  be  strictly  in  accord- 
ance with  its  true  value. 

67.  Numerical  Example.  Assume  that  the  earthwork  com- 
puted in  §  58  is  located  on  a  10°  curve  to  the  left.  How  much 
wnll  be  the  curvature  correction  ?  Copying  from  the  solution  in 
§  58  the  necessary  data  we  have  at  once  the  first  four  columns  of 
the  tabular  form.  Usually  the  last  three  columns  will  be  merely 
added  to  the  form  given  in  §  58.  Since  the  curve  is  to  the  left, 
we  use  the  form  {x^  -  x^.     3R  ^  3  X  573  =  1719.  . 


Station. 

»i 

X, 

Yards. 

x,-x. 

3R 

Curv. 
corr. 

52 

26.4 

13.8 

413 

-12.6 

-  3 

53 

29.1 

18.3 

645 

-10.8 

-  4 

-  7 

54 

35.4 

23.7 

1018 

-11.7 

-  7 

-11 

+  65 

40.5 

27.9 

1488 

-  12.6 

-19 

-17 

55 

30.6 

20.7 

793 

-  9.9 

-  5 

-  8 

Total  curv.  corr.  =  -  43  yardg. 


72 


RAILROAD  ENGINEERING 


The  net  volume  of  the  mass  under  consideration  is  thus  reduced 
to  3,998  cubic  yards.  A  10°  curve  is  rather  unusual.  Since  the 
correction  varies  directly  as  the  degree  of  the  curve,  if  the  above 
curve  were  a  4°  curve  the  correction  would  be  only  0.4  X  43  =  17 
cubic  yards. 

68.     Eccentricity  of  the  Center  of  Gravity  of  a  Side-hill 
Section.     It  will  generally  be  sufficiently  accurate  to  consider,  for 

this  purpose,  that  all  side -hi  11 
sections  are  triangular.  The 
center  of  gravity  of  a  triangle 
lies  on  a  line  joining  the  vertex 
and  the  middle  of  its  base,  and 
at  one-third  of  the  length  of 
this  line  from  the  base.  The 
eccentricity  is  therefore  equal 
the  distance  from  the  center  to 
the  middle  of  the  base  of  the 
triangle  plus  one- third  of  the 
base  of  the  triangle  plus  one-third  of  the  horizontal  projection 
of  that  line.     Applying  this  rule  to  Fig.  46,  we  have 

^=[t-t(-|-x*'')] +-§-[*■'- (4 -t(t+^'))] 


Fig.  46. 


w. 


2  "^  3       12  "*"  6 


4-[4+(^l-^r)] 


(50) 


It  should  be  noted  that  the  grade  triangle  is  not  considered  in  the 
above  solution  ;  therefore  the  volume  of  tlie  grade  prism  should 
not  be  considered  in  applying  Eq.  49.  In  three-level  ground  the 
curvature  correction  will  be  zero  when  Xi  =  cc^.,  but  in  side-hill 
work  the  curvature  correction  is  never  zero  and  it  may  be  a  large 
proportion  of  the  total  volume. 

In  case  the  triangle  lies  wholly  on  one  side  of  the  center,  it 
may  be  similarly  shown  that  the  equation  may  be  written 


RAILROAD  ENGINEERING  73 

This  equation  may  be  derived  directly  from  equation  50  by  con- 
sidering that  when  both  points  are  on  the  same  side  of  the  center, 
the  algebraic  sign  x^.  should  be  changed.  These  various  cases  may 
be  generalized  by  saying  that  when  the  triangle  lies  on  both  sides 

of  the  center,  e  is  always  numerically  equal  to  -—  I  -^  -|-  (a?i  ^  x^.)  I 

in  which  the  form  should  be  {x^  -  Xj.)  or  (r^  -  x^)  according  to 
the  criterion  used  in  §  66.     When  the  triangle  is  on  one  side  only 

e  =  -J— I  -^  +  the  numerical  sum  of  the  two  distances  out  I.     Its 

algebraic  sign  should  be  determined  as  in  §  66. 

CONSTRUCTIVE  EARTHWORK. 

69.  Methods  of  Excavating.  Economical  excavating  depends 
largely  on  the  distance  to  be  hauled  as  well^  as  on  the  character  of 
the  soil.  Side-hill  work  is  usually  done  by  mere  shoveling,  the 
earth  being  loosened  by  picks  or  plows.  When  the  distance  that 
the  earth  must  be  moved  becomes  greater,  wheelbarrows  or  drag 
scrapers  become  economical.  Wheeled  scrapers,  two-wheeled  carts, 
four-wheeled  wagons,  small  cars  drawn  by  horses,  and  heavier  cars 
drawn  in  a  train  load  by  locomotives  successively  become  more 
economical  as  the  distance  increases.  As  the  magnitude  of  the 
work  increases,  thereby  justifying  an  increase  in  the  cost  of  the 
plant  used,  economy  in  the  cost  of  loosening  and  loading  is  ob- 
tained by  using  a  steam-shovel  instead  of  picks  and  plows.  When 
cuts  are  very  deep,  they  are  best  excavated  in  "benches"  whose 
height  will  depend  on  the  method  of  loosening  and  loading. 

70.  Blasting.  Blasting  is  employed  not  only  for  hard  rock 
which  can  only  be  removed  by  such  methods,  but  also  as  a  means 
for  rapidly  loosening  shale  and  even  frozen  earth.  The  explosives 
used  vary  in  their  composition  from  a  high  grade  detonating  ex- 
plosive, such  as  No.  1  dynamite  which  consists  of  75  per  cent 
nitro-glycerine,  to  black  powder  which  is,  comparatively,  "  slow 
burning."  Between  these  extremes  there  are  a  great  multitude 
of  explosive  compounds,  which  consist  of  varying  proportions  of 


74  RAILROAD  ENGINEERING 

explosives  of  the  two  types.  It  has  been  demonstrated  that  a  slow 
burning  explosive  is  made  to  "  detonate  "  if  it  is  exploded  by  means 
of  a  sufficient  volume  of  a  detonating  explosive,  which  means  that 
a  mixture  of  the  two  kinds  has  a  greater  explosive  force  than  the 
sum  of  the  constituents  exploded  separately.  The  choice  of  ex- 
plosive depends  on  the  character  of  the  rock.  A  hard  brittle  rock 
requires  a  detonating  explosive  which  shall  shatter  it.  A  soft  and 
tough  rock  is  best  loosened  by  a  powder  which  acts  more  slowly. 
If  dynamite  is  exploded  in  a  soft  clay  rock  the  hole  will  be  blown 
out,  but  the  great  mass  of  the  rock  is  not  disturbed.  When  the 
center  of  the  mass  of  powder  is  4  feet  from  the  nearest  surface, 
about  2  pounds  of  black  powder  (or  about  J  of  a  pound  of  dyna- 
mite) should  be  used.  The  amount  should  vary  as  the  cube  of  the 
''  line  of  least  resistance,"  i.e.^  if  the  center  of  the  blast  is  10  feet 
from  the  nearest  surface  the  amount  would  be  determined  by  the 
proportion  a?  ;  2  ::  10^  :  4^,  or  ^  =  31  pounds.  In  this  case,  since 
dynamite  is  about  six  times  as  powerful  as  black  powder,  a  little 
over  5  pounds  of  No.  1  dynamite  would  do  as  well.  The  "line  of 
least  resistance"  may  not  be  the  "  nearest  line  to  the  surface"  on 
account  of  seams  in  the  rock  which  modify  its  resisting  power,  but 
the  above  rule  is  about  as  "near  a  fixed  rule  as  can  be  stated.  For 
open  work,  especially  wheH  time  is  not  a  very  important  matter,  it 
is  cheaper  to  use  black  powder,  but  in  tunnel  headings  where  the 
progress  of  the  work  is  limited  by  the  progress  of  the  drillers  it  is 
economical  to  use  dynamite  although  it  is  more  expensive. 

Drilling.  Hand  drilling  when  the  holes  are  vertical  is  best 
accomplished  with  "  churn  drills,"  which  are  heavy  bars  of  iron 
shod  with  a  steel  drill,  which  are  raised  and  dropped,  the  impact 
doing  the  cutting,  the  drill  being  slightly  turned  after  each  stroke. 
From  five  to  fifteen  feet  of  holes,  depending  on  the  character  of 
the  rock,  is  considered  a  fair  day's  work  of  ten  hours.  Oblique 
or  horizontal  holes  must  be  drilled  with  light  drills  of  the  "one- 
man  "  type  or  the  -'  two-man  "  type.  The  one-man  drill  is  worked 
entirely  by  one  man  with  a  light  one-hand  hammer.  With  the 
other  method,  one  man  holds  the  drill,  which  is  perhaps  a  little 
heavier  and  whjch  is  struck  by  another  man,  or  perhaps  by  two, 
using  a  heavy  hammer.  It  has  been  found  that  the  light-hammer 
method  is  more   economical   for  soft  rocks,  the   heavy-hammer 


RAILROAD  ENGINEERING  75 

\ 

method  more  economical  for  hard  rocks,  but  that  the  light-hammer 
method  is  always  quicker  and  is  to  be  preferred  when  limited 
space  and  time  are  matters  of  importance.  Machine  drilh'ng  is  a 
specialty  which  can  only  have  a  very  brief  general  discussion  here. 
Where  the  magnitude  of  the  work  will  justify  it,  it  is  always  more 
economical  pei  foot  of  hole  drilled.  The  plant  is  expensive  both 
in  first  cost  and  maintenance;  part  of  the  expense  is  nearly 
constant  regardless  of  the  number  of  holes  bored,  and  so  it  is  only 
w^hen  the  work  is  extensive  that  the  method  is  advantageous,  but 
under  favorable  circumstances  the  economy  is  very  marked.  For 
open -pit  work  individual  drills  are  used,  but  for  tunnel  headings 
several  drills  are  mounted  on  a  "carriage"  from  which,  after  it  is 
set,  several  holes  may  be  drilled  simultaneously.  Compressed  air 
is  used  to  run  the  drills  in  tunnel  work.  This  serves  the  addi- 
tional purpose  of  furnishing  a  supply  of  pure  cold  air  at  the  place 
where  it  is  most  needed. 

Tamping.  It  has  been  found  that  air  spaces  around  the 
explosive  cause  a  very  material  reduction  in  the  force  of  the  explo- 
sion, therefore  it  is  necessary  to  ram  the  explosive  into  a  solid 
mass  and  then  pack  the  top  of  the  hole.  Iron  bars  should  never 
be  used  for  tamping.  Copper  bars  are  sometimes  used  for  ram- 
ming powder,  but  dynamite  is  most  safely  rammed  with  wooden 
bars.  Clay  is  the  best  tamping  material  where  it  is  available,  but 
sand  or  finely  powdered  rock  will  serve  very  well.  It  has  been 
found  that  when  blasting  under  water  the  weight  of  the  superin- 
cumbent water  is  sufficient  tamping. 

Exploding.  On  small-scale  work,  the  blasts  are  generally 
exploded  by  means  of  a  powder  fuse,  which  is  essentially  a  cord 
which  forms  the  matrix  for  a  train  of  powder,  the  cord  being 
further  protected  by  a  wrapping  of  some  sort.  The  better  plan, 
and  the  one  which  is  used  almost  exclusively  for  extensive  work,  is 
to  explode  a  large  number  of  holes  simultaneously  by  means  of 
electricity.  A  "cap"  containing  a  small  charge  of  fulminate  of 
mercury,  an  expensive  but  very  powerful  explosive,  is  set  in  the 
midst  of  the  larger  mass  of  explosive.  An  electric  current  from 
a  field  battery  is  sent  through  each  cap.  As  the  current  passes 
through  each  cap  it  heats  a  small  platinum  wire  to  redness  or  else 
causes  a  spark  to  jump  across  a  short  gap  in  the  wire.     In  either 


7G  RAILROAD  ENGINEERING 

case  the  fulminate  is  exploded,  wliich  in  turn  explodes  the  main 
charge. 

Cost.  The  cost  of  blasting  is  so  exceedingly  variable,  depend- 
ing on  the  nature  of  the  rock,  depth  of  the  cutting,  and  especially 
on  the  magnitude  of  the  work  and  tlie  methods  employed,  that 
only  the  most  approximate  estimates  can  be  here  given.  Under 
the  most  favorable  circumstances,  deep  cutting,  machine  methods, 
and  a  rock  which  is  brittle  but  not  too  tough,  the  cost  may  fall  as 
low  as  25  cents  per  cubic  yard,  while  with  hand  drilling,  hard  and 
tough  rock,  in  a  shallow  cnt,  the  cost  might  easily  rise  to  %\.  per 
cubic  yard.  It  would  indicate  exceptionally  unfavorable  circum- 
stances, bad  management,  or  possibly  an  excessive  price  for  com- 
mon labor,  if  the  cost  should  rise  above  this  figure. 

71.  Formation  of  Embankments.  Experience  has  shown 
that  when  earth  is  excavated  and  piled  in  embankments  its  vol- 
ume will  at  first  be  more  than  the  original  measured  volume  but 
that  it  will  finally  shrink  to  about  90  per  cent  of  its  original 
volume.  The  percentage  of  shrinkage  is  a  very  uncertain  quan- 
tity, as  it  depends  on  the  kind  of  earth,  on  the  method  employed 
in  forming  the  embankment  and  on  the  time  elapsed  between 
construction  and  the  measurement  of  what  is  supposed  to  be  the 
settled  volume.  Material  dumped  from  a  trestle  will  first  have  a 
volume  considerably  in  excess  of  its  final  volume  and  it  will  take 
Several  months  and  even  years  to  shrink  to  its  final  volume.  On 
the  other  hand,  if  an  embankment  is  formed  in  very  thin  layers, 
each  of  which  is  packed  down  by  the  process  of  unloading  the 
succeeding  layer,  there  will  be  but  little  shrinkage  after  the 
embankment  is  finished,  but  more  material  than  the  volume  as 
measured  in  the  cut  will  be  required  to  form  that  volume  of 
embankment.  Broken  rock,  formed  into  an  embankment,  will 
have  a  volume  about  80  per  cent  greater  than  the  mass  of  solid 
rock  from  which  it  is  taken. 

It  is  frequently  specified  that  embankments  are  to  be  made 
to  a  somewhat  higher  elevation  than  the  plan  of  the  road  calls  for, 
so  that  the  expected  shrinkage  will  reduce  the  embankment  to  the 
desired  level.  Since  the  contractor  is  paid  by  the  cubic  yards  of 
material  excavated  and  is  required  to  dispose  of  excavated  mate- 
rial as  required,  it  is   generally  specified  that  the  amount  of  this 


KAILROAD  ENGINEERING  77 

excess  of  height  of  embankments  is  left  to  the  discretion  of  the 
engineer  who  decides  the  question  during  the  progress  of  the  work 
and  after  he  has  had  an  opportunity  to  jndge  of  the  material  after 
excavation  is  under  way.  When  embankments  are  placed  on  side- 
hills,  the  surface  should  be  first  plowed  or  have  trenches  dug 
along  the  slope  so  that  the  embankment  shall  not  slip  down  the 
hill.  A  ditch  dug  at  the  base  of  each  slope  will  drain  the  sub- 
soil and  may  prevent  a  dangerous  and  costly  disintegration  of  the 
embankment.  Thickening  the  layers  of  an  embankment  on  the 
outside  somewhat  so  that  the  layers  will  be  concave  upward  may 
also  present  sliding  of  the  layers  on  each  other.  When  the  plans 
call  for  a  very  long  and  high  embankment,  it  is  sometimes  best 
to  construct  first  a  trestle  and  operate  the  road  over  it.  The 
trestle  should  have  a  life  of  at  least  five  or  six  years,  and  during 
that  time  material  can  be  brought  from  some  excavation,  perhaps 
several  miles  away,  where  it  was  perhaps  loaded  with  a  steam 
shovel,  hauled  by  the  train  load,  dumped  with  an  "unloader," 
and  allowed  all  the  required  time  to  settle,  the  whole  being  done 
for  a  cost  per  yard  far  less  than  it  would  have  cost  during  the 
original  construction.  The  method  has  the  added  advantage  of 
permitting  the  road  to  be  quickly  opened  for  traflic  and  permitting 
it  to  quickly  get  on  an  earning  basis,  for  such  a  trestle  can  be 
built  more  quickly  than  a  very  high  embankment. 

72.  Classification  of  Earthwork,  One  of  the  most  fruitful 
sources  of  legal  contention  between  a  contractor  and  his  employer 
is  the  classification  of  excavated  material  when  the  work  is  paid 
for  according  to  the  classification  of  the  material  excavated.  It  is 
not  only  true  that  there  is  an  insensible  gradation  from  the  softest 
of  earth  to  the  hardest  of  rock,  but  a  material  which  is  very  hard 
when  first  exposed  will  sometimes  crumble  up  after  a  very  short 
exposure  to  the  atmosphere.  It  is  even  true  that  some  kinds  of 
rock  which  are  very  soft  when  first  taken  out  harden  after  exposure 
to  the  air,  but  this  class  of  phenomena  never  has  any  influence  on 
mere  blasting  for  excavation.  To  avoid  these  disputes,  some  rail- 
roads require  their  contractors  to  satisfy  themselves  as  to  the  char- 
acter of  the  material  to  be  excavated  and  then  to  make  a  single  bid 
per  yard  which  shall  include  whatever  material  is  encountered. 
With  all  its  advantages,  this  throws  all  the  uncertainty  on  the  con- 

87 


78  RAILROAD  ENGINEERING 

tractor,  and  unless  the  competition  is  very  great  and  the  bidding 
close  the  contractor  will  usually  add  so  much  to  cover  that  uncer- 
tainty that  the  railroad  will  pay  more  than  it  would  on  a  classified 
basis. 

The  classification  is  usually  made  threefold — (1)  solid  rock,  (2) 
loose  rock,  including  shale  and  hard-pan,  and  (3)  earth.  Solid  rock 
includes  only  such  material  as  cannot  be  removed  except  by  blasting, 
when  it  is  found  in  masses  exceeding  one  cubic  yard.  Loose  rock 
includes  boulders  which  are  more  than  one  cubic  foot  in  volume 
and  less  than  one  cubic  yard;  also  stratified  rock  occurring  in 
layers  of  not  more  than  six  inches,  when  they  are  separated  by 
strata  of  clay;  also  all  material  (not  classified  as  earth)  which  can 
be  loosened  with  a  pick  and  bar  and  which  "  can  be  quarried  with- 
out blasting  although  blasting  may  occasionally  be  resorted  to." 
"  Earth  "  includes  all  material  not  considered  above — boulders  not 
over  one  cubic  foot  in  volume,  all  clay,  sand,  gravel,  loam,  decom- 
posed rock  and  slate,  and  all  materials  which  can  be  loosened  for 
loading  by  a  plow  with  two  horses,  or  such  as  one  picker  can 
keep  one  shoveler  busy.  A  brief  consideration  of  the  above  classi- 
fication, which  is  compiled  from  the  best  authorities  available, 
shows  the  infinite  opportunities  for  dispute  as  to  classification. 

TUNNELS  —  SURVEYING. 

73.  Charac|;er  of  Surveying.  There  are  few  kinds  of  sur- 
veying for  engineering  work  where  accuracy  is  of  such  high  finan- 
cial value  and  where  it  is  so  difficult  to  accomplish  as  it  is  in 
tunnel  work.  By  the  very  nature  of  the  case  a  tunnel  is  usually 
located  in  a  region  where  it  is  very  rough  and  all  the  surface  sur- 
veys must  be  made  on  very  steep  slopes  where  accurate  measure- 
ments are  exceedingly  difficult.  The  surveys  in  the  tunnel  itself 
are  made  in  cramped  quarters  where  light  is  artificial  and  the 
atmosphere  is  perhaps  smoky.  The  difficulties  will  be  elaborated 
as  the  methods  for  obviating  them  are  discussed.  Tunnels  are 
generally  excavated  from  each  end.  A  very  small  error  at  either 
end  will  accumulate,  especially  if  the  tunnel  is  very  long^  until 
when  the  two  headings  meet  there  may  be  an  offset  which  might 
actually  necessitate  a  small  reversed  curve  in  the  alignment. 
Therefore  only  the  most  refined  measurements  for  distance,  the 


RAILROAD  ENGINEERING  79 

most  refined  leveling  between  the  ends  of  the  tunneling  and  the 
repeated  measurements  of  all  horizontal  angles  or  the  most  precise 
prolongation  of  lines  are  to  be  used.  All  such  work  should  be 
repeated  and  checked  until  the  probable  error  of  the  work  is  so 
small  that  such  error  as  may  remain  has  no  financial  importance. 
The  cost  of  such  refined  work  is  amply  justified,  because  the  lack  of 
it  may  result  in  an  error  whose  financial  value  might  be  very  great. 

74.  Surface  Surveys.  The  relative  position  of  the  two  ends 
of  the  tunnel  is  first  determined,  t.^.,  the  azimuth  and  length  of  a 
line  joining  the  two  ends  and  the  relative  elevation.  Usually  a 
line  is  run  on  the  surface  which  will  be  at  every  point  exactly 
over  the  center  line  of  the  tunnel.  When  the  tunnel  is  perfectly 
straight  throughout,  this  is  comparatively  easy.  Any  curvature 
in  the  tunnel  complicates  the  surveying  greatly.  A  permanent 
station,  from  which  a  long  sight  can  be  run  into  the  tunnel,  is 
placed  at  each  end.  Then  intermediate  permanent  stations  are  set 
so  that  adjacent  stations  are  intervisible.  These  stations  are  first 
set  approximately  on  line  and  then  by  repeated  adjustments  they 
are  all  set  exactly  on  line.  Any  intermediate  shaft  can  then  be 
located  from  the  adjacent  stations. 

Distance.  The  distance  is  sometimes  determined,  as  in  geo- 
detic surveying,  by  triangulation  and  the  measurement  of  a  base  line. 
Some  of  the  great  Alpine  tunnels  have  been  measured  in  this  way. 
But  for  simpler  work  a  direct  measurement  is  made  with  a  tape. 
Since  the  slopes  are  usually  very  steep,  it  becomes  impracticable 
to  hold  any  very  great  length  of  the  tape  truly  horizontal.  It  is 
then  also  necessary  to  plumb  down  from  the  down-hill  end  of  the 
tape  to  the  ground.  This  is  troublesome  and  also  introduces  an 
element  of  inaccuracy.  And  therefore  "slope  measurements"  are 
often  made,  measuring  the  slope  distance  between  carefully  marked 
points  and  at  the  same  time  determining  the  difference  of  elevation. 
A  simple  geometrical  calculation  then  determines  the  true  hori- 
zontal distance.  These  marks  may  consist  of  needles  set  in  woodeD 
plugs  supported  on  ordinary  surveying  tripods. 

Levels.  The  above  method  includes  the  leveling.  But  if 
the  ordinary  niethod  of  leveling  is  used,  especial  care  must  be 
taken,  since  the  slopes  are  very  steep  and  the  vertical  distances  to 
be  overcome  very  great. 


80  RAILROAD  ENGINEERING 

75.  Underground  Surveys.  Station  marks,  corresponding 
to  the  stakes  of  ordinary  surveys,  cannot  usually  be  placed  in  the 
bottom  of  the  tunnel  since  they  would  be  very  quickly  disturbed 
or  covered  over  with  debris.  If  the  tunnel  is  timbered,  the  eas- 
iest method  is  to  place  the  marks  on  the  timbering,  but  this  should 
not  be  done  unless  the  timbering  is  very  firmly  in  place  and  is  not 
liable  to  be  shifted.  The  better  plan  is  to  drill  a  hole  in  the  roof  of 
the  tunnel,  insert  a  wooden  plug,  and  then  set  in  the  wood  a  small 
hook  or  nail  which  marks  the  exact  point.  Occasionally  such 
marks  are  placed  on  the  side  of  the  tunnel.  "When  placed  in  the 
roof  there  is  the  advantage  that  a  plumb  line,  which  must  be  illu- 
minated  by  a  lantern,  may  be  swung  from  the  hook  or  nail.  A  still 
better  device  is  a  plumb  bob  hung  by  a  pair  of  cords  attached  to 
a  "gimbel  joint"  on  the  bob.  The  bob  has  a  little  reservoir  for 
oil  and  a  wick  exactly  in  the  center  which  will  furnish  a  flame 
which  may  be  seen  as  far  as  necessary  and  which  may  be  bisected 
by  the  cross  hairs  of  the  transit  with  great  accuracy.  Such 
*•'  sights"  can  be  reproduced  whenever  desired  with  great  confidence 
that  there  is  no  appreciable  variation.  When  a  mere  plumb  line 
is  used  to  sight  at,  it  must  be  illuminated  by  some  sort  of  lantern. 
This  may  be  done  by  using  a  lantern  with  a  ground  glass  which  is 
placed  behind  the  line,  which  is  seen  by  its  contrast  against  the 
illuminated  background.  If  an  ordinary  lantern  is  used,  it  should 
be  placed  nearly  in  front  of  the  line  and  pointing  away  from  the 
transit,  so  that,  without  being  seen  from  the  transit,  it  illuminates 
the  face  of  the  line  which  then  shows  light  against  the  darkness  of 
the  tunnel. 

The  leveling  must,  of  course,  be  done  with  the  level  rod  in- 
verted so  as  to  obtain  the  distance  from  the  station  point  down  to 
the  line  of  sight.  Of  course  this  makes  a  corresponding  difference 
in  the  calculations  which  must  be  carefully  watched  to  avoid  a 
blunder  due  to  this  change.  This  may  be  avoided  by  always  plac- 
ing a  minus  sign  before  any  rod  readings  so  taken,  and  then  fol- 
lowing the  old  rule  of  algebraically  adding  backsights  and  sub- 
tracting foresights  and  intermediate  sights.  Various  devices  are 
required  to  meet  special  conditions  which  test  the  inventive  inge- 
nuity of  the  engineer. 


RAILROAD  ENGINEERING  81 

76.  Surveying  Down  Shafts.  In  the  case  of  very  long  tun- 
nels  it  sometimes  seems  advisable  to  sink  shafts  at  one  or  more 
points  on  the  line  of  the  tunnel,  and  when  they  have  been  sunk  to 
the  required  depth,  proceed  to  dig  out  the  tunnel  in  each  direction. 
For  such  work  it  becomes  necessary  to  determine,  at  the  bottom  of 
the  shaft,  elevation,  distance  and  alignment.  If  the  shaft  is  ver- 
tical, as  is  usually  but  not  always  the  case,  the  elevations  are  most 
readily  carried  down  the  shaft  by  means  of  a  steel  tape  by  methods 
which  are  obvious.  Distance,  which  means  in  this  case  the  longi- 
tudinal position  in  the  alignment  of  the  road  of  any  given  point, 
is  readily  transferred  from  the  surface  to  the  level  of  the  tunnel 
by  a  very  obvious  application  of  the  results  of  the  next  process  to 
be  described.  Transferring  the  alignment  with  accuracy  requires 
the  utmost  care  and  ingenuity.  In  principle  it  is  very  simple. 
Two  heavy  plumb  bobs  are  hung  on  steel  wires  which  are  long 
enough  to  reach  from  the  surface  to  the  tunnel.  At  the  surface 
they  are  placed  on  a  line.  Theoretically  they  should  be  on  a  line 
at  the  level  of  the  tunnel.  If  a  transit  is  so  placed  in  the  tunnel 
that  its  line  of  collimation  passes  simultaneously  through  both 
wires,  it  is  in  the^ine  of  the  tunnel.  Such  is  the  simple  outline; 
some  of  the  difficulties  are  as  follows: 

Although  the  wires  are  set  as  far  apart  as  possible  along  the 
line  of  the  tunnel,  the  distance  is  absolutely  limited  by  the  size  of 
the  shaft.  Any  minute  error  in  the  location  of  these  lines  (say 
eight  feet  apart)  will  be  greatly  magnified  when  the  headings  are 
run  out  6,000  or  7,000  feet  in  each  direction  from  the  base  of  the 
shaft,  as  was  done  in  the  case  of  the  Hoosac  tunnel.  The  currents 
of  air  up  a  tunnel  shaft  have  considerable  effect  in  swaying  the 
wire  from  a  true  vertical.  In  the  case  of  the  Tamarack  shaft, 
4,250  feet  deep,  the  wires  were  0.11  foot  farther  apart  at  the  bot- 
tom than  at  the  top.  The  discrepancy  in  that  direction  had  no 
effect  on  the  alignment,  but  if  the  wires  had  an  error  whose  com- 
bined effect  in  that  direction  was  0.11  foot,  the  lateral  error  while 
unknown  was  perhaps  as  much  or  more.  The  uncertainty  was 
therefore  in  that  case  very  great.  Incasing  such  wires  for  the 
whole  distance  in  a  box  reduces  the  effect  of  air  currents.  The 
plumb  bobs  are  swung  in  pails  of  water  or  oil  at  the  bottom  and 
their  locations  noted  as  carefully  as  possible,  taking  the  mean  posi- 


82  RAILROAD  ENGINEERING 

tiori  of  the  vibrations  which  cannot  be  altogether  overcome.  Marks 
are  then  set  at  the  bottom  of  the  shaft  (but  in  the  roof  of  the 
tunnel)  from  which  plumb  lines  can  be  hung.  A  transit  can  then 
be  set  by  trial  so  that  its  line  of  collimation  simultaneously  passes 
through  both  wires. 

TUNNEL  DESIGN. 

77.  Cross-Sections.  The  variety  in  the  cross-sections  which 
have  been  adopted  is  due  to  the  fact  that  there  are  no  absolute  re- 
quirements which  determine  the  design  except  in  a  general  way. 
If  the  tunnel  passes  through  such  very  soft  soil  that  there  is  ex- 
cessive pressure  the  form  should  be  circular  or  nearly  so.  While 
the  size  of  the  rolling  stock  is  in  one  sense  a  limitation,  yet  the 
clearance  should  be  considerable,  pswtly  for  the  reason  of  allowing 
something  for  a  possible  settlement  of  the  lining.  A  majority  of  the 
sections  used  have  a  semi-circle  or  semi-ellipse  surmounting  a  rect- 
angle or  trapezoid.  Even  when  the  ground  is  so  soft  that  lining  is 
required  not  only  at  the  top  but  also  at  the  sides  and  bottom,  the 
same  general  shape  will  be  used  except  that  the  straight  lines  will 
be  replaced  by  arcs  of  circles  concave  to  the  center  of  the  tunnel. 
Illustrations  of  cross -sections  will  be  shown  under  a  subsequent 
section. 

A  tunnel  almost  invariably  strikes  one  or  more  veins  of  water 
which  immediately  begin  to  discharge  into  the  tunnel,  which  there- 
after becomes  the  drainage  outlet  for  such  water.  This  necessi- 
tates an  adequate  provision  for  drainage.  In  a  double  track  tunnel 
the  drain  will  usually  be  placed  between  the  two  tracks,  but  with 
single-track  tunnels  they  must  necessarily  be  placed  on  each  side. 
Fig.  48  will  illustrate  this  feature. 

78,  Grade.  Many  tunnels  are  situated  at  the  summit  of  two 
grades,  which  are  very  probably  the  ruling  grade  of  the  road.  In 
such  a  case  it  is  possible  to  make  the  ends  of  t|ie  tunnel  at  practi- 
cally the  same  level  and  have  no  grade  in  the  tunnel  except  a  slight 
grade  for  drainage.  There  should  be  no  grade  summit  in. 
the  tunnel.  Grade  for  drainage  should  never  be  omitted — about 
0.2  per  cent  grade  is  required.  But  tunnels  are  frequently  neces- 
sary as  parts  of  a  grade  which  is  very  possibly  the  ruling  grade  of 
the  line.     In  such  cases  the  grade  should  be  very  materially  re- 


RAILROAD  ENGINEERING 


83 


duced  while  running  through  the  tunnel.  The  atmospheric  resist- 
ance in  a  tunnel  is  greater,  the  rails  are  apt  to  be  wet  and  slippery 
and  the  tractive  power  therefore  less,  while  the  consumption  of  the 
limited  supply  of  oxygen  by  the  locomotive  and  the  poisonous 
fumes  cast  off,  especially  when  the  engine  is  working  hard,  is  a 
source  of  actual  danger  to  the  engine  crew  and  even  to  the  pas- 
sengers. Therefore  a  generous  reduction  of  grade  should  be  made, 
although  the  precise  amount  of  compensation  required  is  hardly 
computable. 

79.     Lining.     The  lining  required  varies  from  no  lining,  such 
as  may  be  permitted  when  the  rock  is  so  firm  that  it  will  be  abso- 


Fig.  47.    Connection  witli  Shaft,  Church  Hill  Tunnel. 

lutely  self  sustaining  and  will  not  disintegrate  upon  exposure  to 
the  weather,  and  a  lining  of  the  very  heaviest  and  strongest  cut- 
stone  masonry  which  should  be  used  when  the  ground  is  subject 
to  extensive  settling.  This  condition  is  far  worse  than  any  mere 
fluid  pressure.  Many  American  tunnels  have  been  constructed 
with  a  permanent  lining  of  timber,  such  as  is  illustrated  in  Fig. 
47.  In  other  cases  the  cross-section  of  a  tunnel  has  purposely 
been  made  somewhat  larger  than  necessary,  so  that  when  the  tim- 
ber lining  required  renewal  a  masonry  lining  could  be  built  inside 
of  the  timber  lining  without  encroaching  on  the  required  clear 
cross-section  and  without  requiring  any  disturbance  of  the  timber 


84 


RAILROAD  ENGINEERING 


lining.  In  this  way  the  heavy  expense  of  the  masonry  lining  could 
be  deferred  until  a  time  when  the  road  would  probably  be  better 
able  to  pay  for  it.  True  economy  requires  the  best  of  cement 
masonry.  When,  on  account  of  an  unintentional  fall  of  rock  out- 
side  of  the  nominal  excavation  lines  a  space  would  be  left  between 
the  lining  and  the  line  of  the  excavation,  such  space  should  be 
filled  with  broken  stone  well  packed  in  or  even  with  concrete  or 
solid  masonry. 


Fig.  48. 

80.  Portals.  Although  no  calculations  can  be  made  to  de- 
termine the  forces  acting  on  a  portal,  it  is  readily  seen  that  they 
are  sometimes  very  great,  as  they  must  often  prevent  a  tendency  of 
the  face  of  the  mountain  to  slide  down  over  the  tunnel  outlet.  In 
Fig.  48  is  shown  a  typical  portal.  These  are  sometirhes  made  very 
elaborate  architecturally,  but  the  leading  feature  of  the  design  must 
be  its  massiveness.  It  must  act  as  a  retaining  wall  against  the 
direct  action  of  the  slope.  If  there  is  also  a  considerable  stretch 
of  open  cut  at  the  entrance  to  the  tunnel,  then  the  design  is  really 
simplified  by  walls  on  the  sides  of  the  cut  which  will  act  as  but- 
tress walls  to  the  portal.  Some  of  the  most  difficult  construction 
of  a  tunnel  may  occur  at  the  portals.     It  is  here  that  the  thickness 


RAILROAD  ENGINEERING 


85 


of  the  natural  ''roof"  of  the  tunnel  runs  out  to  piactically  zero. 
Considerable  thickness  is  required  before  it  will  become  self-sus- 
taining enough  to  give  opportunity  to  place  the  timbering.  The 
surface  soil  may  also  be  so  loose  that  the  excavation  below  starts 
a  landslide.  Therefore  a  very  heavy  timber  frame  must  be  con- 
structed outside  of  the  line  of  the  proposed  portal  and  must  be 
very  heavily  braced  to  withstand  a  probable  tendency  to  a  landslide. 
In  one  case  a  shaft  was  sunk  a  short  distance  from  the  portal; 
tunnel  excavation  and  permanent  masonry  lining  was  at  once  com- 
menced, running  back  toward  the  portal.  As  the  surface  was  ap- 
proached the  thin  roof  was  so  thoroughly  supported  that  no  serious 
difficulty  was  encountered  from  a  landslide. 

TUNNEL  CONSTRUCTION. 

81.  General  Principles.  A  large  majority  of  tunnels  require 
a  lining  because  the  material  through  which  they  are  excavated 
cannot  be  depended  on  to  be  self-sustaining.  Except  in  sub-aqueous 


Cross    Section. 

Fig.  49. 


Lonqitudinoi    Section. 

Fig.  50. 

work,  all  material  is  self-sustaining  over  a  small  area  and  for  a 
short  time,  a  time  long  enough  so  that  after  a  small  area  has  been  ex- 
posed a  support  even  though  temporary  may  be  placed  which  will 
prevent  a  fall  at  that  place.  Since  there  are  all  gradations  in  mate- 
rial from  the  hardest  of  rock  to  the  softest  of  quicksand,  there  are 
likewise  gradations  in  the  methods  to  be  adopted,  in  the  prompt- 
ness  with  which  timbering  must  be  placed  to  support  exposed 
areas  and  also  in  the  extent  of  area  which  may  be  safely  exposed 
before  timbering  is  placed.  All  methods  agree  in  excavating  one 
or   more  headings    in    advance  of  the  full   sectional  excavation. 


86 


RAILROAD  ENGINEERING 


These  headings  are  sometimes  made  at  the  top,  sometimes  at  the 
bottom  and  sometimes  at  the  two  lower  corners.  One  good  effect 
of  such  headings  is  to  drain  the  soil  in  advance  of  the  main  exca- 
vation and  thus  facilitate  the  sub- 
sequent work.  These  headings 
are  then  enlarged  until  at  last  the 
full  sectional  area,  including  that 
required  for  the  lining,  is  ob- 
tained. The  construction  of  the 
lining  follows  closely,  so  that  in 
a  stretch  of  perhaps  less  than  80 
feet  may  be  seen  all  stages  of  the 
work,  from  the  initial  heading  to 
the  finished  tunnel  completely 
lined. 

82.  riethods.  The  limita- 
tions  of  this  paper  will  not  permit 
a  complete  discussion  and  descrip- 
tion of  the  various  methods  which 
are  used  in  this  work.  Some  illustrations  are  shown  to  give  the 
student  such  a  grasp  of  the  gen- 
eral principles  involved  that  a 
generous  application  of  common 
sense  may  enable  him  to  accom- 
plish some  of  the  plainer  and 
simpler  problems.  The  timber- 
ing must  be  so  designed  and 
placed  that  there  will  be  little 
or  no  tendency  for  the  pieces  to 
slip  on  each  other  and  that  any 
added  pressure  will  only  bind 
the  framing  still  tighter  to- 
gether. The  timbering  should 
never  fail  except  by  absolute 
crushing,  and  its  cross-section 
should  be  made  such  that  it  may 
withstand  any  probable  pressure 
tions  will  illustrate  this. 


Fig.  52. 
An  inspection  of  the  illustra- 


RAILROAD  ENGINEERING 


87 


Fig.  53. 


Much  of  the  difficulty  of  tunnel  work  arises  from  the  limited 
space  in  which  the  work  must  be  done.  A  well-devised  system  of 
removing  excavated  material  as  rapidly  as  it  is  loosened  and  of 
handling  the  materials  for  the 
lining  and  placing  them  in  posi- 
tion is  therefore  an  absolute 
necessity.  The  use  of  small  cars 
on  rails  is  usually  advisable. 
With  a  tunnel  of  any  consider- 
able length,  artificial  ventila- 
tion during  construction  is  nec- 
essary, especially  if  blasting  is 
required.  As  before  mentioned, 
compressed  air  may  be  used  to 
operate  the  drills  for  blasting 
and  this  may  supply  the  need. 
But  where  no  blasting  is  re- 
quired, and  sometimes  even 
when    compressed    air   is   used, 

ventilation  by  fans  is  necessary.  The  fans  and  engines  for  oper- 
ating them  are  of  course  placed  outside  the  tunnel  and  the  fresh  air 
is  discharged  from  a  pipe  where  desired. 

TRESTLES. 

A  trestle  consists  of  two  essential  parts,  the  sub-structure 
framework  and  the  floor  system.  Since  the  floor  system  is  essen- 
tially independent  of  the  sub-structure,  it  will  be  separately  described. 
There  are  two  systems  of  building  the  sub-structure,  by  piling  and 
by  timber  frames. 

83.  Pile  Trestles.  These  are  Hmited  in  height  to  the  length 
of  a  single  pile  which  may  safely  be  used.  The  length  of  pile 
required  must  include  the  necessary  depth  to  which  they  must  be 
driven.  On  this  account  30  feet  above  the  ground  is  about  the 
limit  of  height  of  a  pile  trestle.  With  exceptionally  long  piles 
higher  pile  trestles  might  be  built,  but  framed  bents  would  be 
preferable.  Usually  four  piles  are  considered  sufficient  for  single 
track,  although  more  are  sometimes  used.  The  inner  piles  are 
always  made  vertical  but  the  outer  piles  are  sometimes  battered  so 


88  RAILROAD  ENGINEERING 

as  to  give  the  trestle  a  greater  resistance  against  a  lateral  thrust. 
For  a  high  trestle  (greater  than  10  feet)  this  thrust  is  best  taken 
up  by  sway  bracing.  The  piles  are  surmounted  by  a  cap  which  is 
generally  10X12  in.,  or  perhaps  12X12  in.  A  still  better  form 
of  cap  is  the  "split  cap/*  which  consists  of  two  pieces  bolted  to- 
gether as  shown  in  the  detail  of  Fig.  56.  Other  methods  of  join- 
ing the  cap  to  the  piles  are  illustrated  herewith.  The  construction 
using  drift  bolts  is  perhaps  the  cheapest  and  most  quickly  erected, 
but  it  has  the  disadvantage  that  repairs  are  difficult,  and  if  the  tres- 
tle is  merely  temporary  it  is  almost  impossible  to  remove  it  without 
ruining  the  timber  for  future  use.  The  mortise  and  tenon  joint 
is  perhaps  the  most  common  for  good  practice.  The  piles  should 
be  not  less  than  14  in.  in  diameter  at  the  butt  and  7  in.  at  the  top, 
exclusive  of  bark,  which  should  be  removed  before  driving.  The 
soft  durable  woods  such  as  cedar,  cypress,  pine  and  redwood  are 
best  for  piles  that  are  not  driven  in  a  stream  where  they  may  be 
subject  to  the  blows  of  floating  ice.  The  oaks  are  stronger  but 
are  less  durable  in  the  ground.  The  caps  are  preferably  made  of 
hard  wood  such  as  oak  or  yellow  pine.  They  should  be  about  14 
ft.  long  for  single  track.  The  sway  braces  are  generally  3X12  in. 
and  are  usually  spiked  with  |-in.  spikes  8  in.  long. 

84.  Pile  Driving.  Piles  are  usually  driven  by  means  of  a 
hammer  weighing  2,000  to  3,000  pounds,  which  is  raised  between 
guides  to  a  height  of  perhaps  25  feet  and  allowed  to  drop  onto  the 
head  of  the  pile  which  is  suitably  set  between  the  guides.  A  very 
cheap  way  is  to  raise  the  hammer  by  horse  power,  and  then  loosen 
a  clutch  which  allows  the  hammer  to  fall  freely.  A  still  better 
way  is  to  use  a  portable  engine  which  winds  the  hoisting  rope 
around  a  drum.  Sometimes  the  falling  hammer  is  required  to 
draw  the  rope  and  unwind  the  drum  as  it  falls.  On  the  one  hand, 
this  obviates  the  use  of  a  clutch  and  even  permits  more  rapid  blows, 
but  on  the  other  hand,  the  force  of  each  blow  is  very  materially 
weakened  and  the  method  may  be  used  by  a  dishonest  contractor 
to  falsely  indicate  a  high  resisting  power  of  the  pile.  Excessive 
driving  has  been  known  to  fracture  a  pile  underground  and  render 
it  almost  useless.  The  action  of  the  hammer  splinters  the  top  of 
the  pile,  causing  it  to  "broom."  This  action  very  greatly  reduces  the 
effectiveness  of  the  driving.    This  is  largely  prevented  by  chamfering 


RAILROAD  ENGINEERING 


89 


off  the  top  of  the  pile  and  driving  on  a  wrought-iron  ring,  which  has 
a  section  of  about  ^X2  in.  and  of  a  suitable  diameter.  The  fre- 
quent removal  of  all  crushed  wood  from  the  head  of  the  pile  by 
means  of  an  adze  is  amply  justifiable  in  spite  of  the  delay  caused. 
Piles  should  be  driven  until  their  resistance  as  indicated  by  the 
penetration  for  a  single  blow  is  as  great  as  is  required.  The  most 
commonly  used  formula  is  that  known  as  the  "Engineering  News" 
formula,  which  when  used  for  ordinary  hammer  driving  is  as  follows: 

2wh 


R  = 


*  +  l 


(52) 


In  this  formula  R  is  the  safe  load  on  the  pile,  iv  is  the  weight  of 
the  hammer,  both  in  pounds,  h  is  the  height  of  the  fall  in  feet,  and 


Fig.  54. 


Fig.  55. 


s  is  the  penetration  in  inches  of  the  pile  during  the  last  blow. 
Sometimes  the  average  penetration  during  the  last  five  blows  will 
give  a  more  reliable  value. 

Example  1.  A  pile  was  driven  with  a  2,500-lb.  hammer 
until  the  total  penetration  during  the  last  five  blows  was  13  inches. 
During  those  blows  the  hammer  dropped  23  feet.  How  much  is 
the  safe  load? 

2wh    2X2,500X23     115,000     ^,  ^.,  , 

-TT=-rr^7T^iT3rr  ='—TT'  =  ^^'^^^  pounds. 
5+1       (|X13)  +  1  3.6 

Example  2.  It  is  required  to  drive  piles  with  the  above  ham- 
mer until  the  indicated  resistance  is  25,000  lb.  What  should  be 
the  average  penetration  during  the  last  five  blows,  the  fall  being 

then  22  feet? 

2ich    2X2,500X22     110,000 


25,000  = 


^  +  1 

110,000 

25,000 


-V+l  .9+1 

—  1  =3.4  inches. 


90 


RAILROAD  ENGINEERING 


Another  form  of  pile  driver  is  that  known  as  the  "steam  pile 
driver."    This  consists  essentially  of  a  hammer  which  is  directly  at- 
tached to  a  piston  in  a  steam  cylin- 
der.   The  hammer,  weighing  about 
5,500  pounds,  is  raised  the  height 
of  the  cylinder,  which  is  about  40 
inches,  and  then  falls  freely.     Al- 
though the  fall  is  so  much  less  the 
blows  are  very  rapid — about  75  to 
ninP,/i/lliii\}\iiiin}j\niilu}pjn  80  per  minute.    The  practical  effect 
W  W        'wvl  U      of  this  is  that  the  soil  does  not  have 

Fig.  56.  time  to  settle  between  the  blows 

and  the  penetration  is  more  easily 
accomplished,  while  the  ultimate  resistance  is  as  great  as  before. 
On  this  account  the  constant  "1"  in  the  denominator  in  equation 
52  is  changed  to  0.1  and  the  formula  then  becomes 

2w}i 


R  = 


5+0.1 


(53) 


FRAMED  TRESTLES. 


85,  General  Form.  Although  there  are  multitudin9us  varia- 
tions in  the  details  of  construction,  a  very  large  proportion  of 
framed  trestles  are  constructed  substantially  in  accordance  with 
the  typical  design  shown  in 
Fig.  57.  The  outer  posts  are 
generally  battered  about  1:6; 
the  cap  and  sill  are  mortised 
to  the  posts,  although  split 
sills  and  caps  can  be  used  ad- 
vantageously. The  sway  brac- 
ing should  be  bolted  on.  Al- 
though the  mortise  and  tenon 
joint  are  most  commonly 
used,  there  are  many  other 
designs.    The  "plaster  joint" 

is  one  of  the  most  common.  This  consists  of  two  pieces  of  3-in. 
plank  which  are  placed  on  each  side  of  the  joint  as  in  Fig.  58,  and 
are  bolted  through  and  through.    This  form  has  the  merits  of 


Fig.  57. 


RAILROAD  ENGINEERING 


91 


cheapness  and  facility  for  taking  out  and  renewing  any  decayed  or 
injured  piece.  Iron  plates  are  sometimes  used  in  a  similar  manner. 
Dowels  and  drift  bolts  are  also  used,  but  as  mentioned  before  have 
many  objections. 

86.  Multiple    Story    Construction.    A    single-story    framed 
trestle  should  not  be  made  over 

25  or  30  feet  high.     Additional  /*MA<f  ^/^j^j^ 

height  is  obtained  by  dividing  the 

height  into  two  or  more  stories. 

Then  since  all  the  upper  stories 

must  be  of  uniform  height  the  /  ®  /  ?  0=liMH> 

odd  amount  must  go  to  the  lower 

story,  as  is  illustrated  in  Figs.  Fig.  58. 

59  and   60.    Some  plans  have 

these  stories  absolutely  independent  of  each  other.     This  simplifies 

the  construction  and  makes  repairs  easy,  but  the  trestle  will  be 

lacking  in  stiffness.  These  illustrations  should  be  studied  with 
special  reference  to  the  design  of  the  lateral 
bracing  of  the  individual  bents  and  also  the 
longitudinal  bracing  of  the  trestle  as  a  whole. 
Note  that  the  lateral  bracing  always  runs  to 
some  point  where  two  or  more  pieces  inter- 
sect, and  when  possible  it  is  so  designed  that 
even  the  intermediate  points  are  a  common 
point  for  several  pieces.  A  thorough  bolting 
at  these  points  greatly  stiffens  the  structure. 
The  span  between  the  bents  varies  from  10 
feet  to  18  feet.  For  high  trestles  economy 
requires  that  the  number  of  bents  shall  be 
reduced  as  much  as  possible,  which  means 
that  the  spans  should  be  increased.  But  this 
increases  the  requirements  for  the  floor  sys- 
tem, and  also  the  load  to  be  carried  by  each 
bent.  18  feet  is  about  the  safe  limit  for  railroad 
rolling  stock  on  untrussed  wooden  floor  beams. 

87.  Foundations.  Trestles  are  frequently  to  be  classed  as 
"temporary"  structures.  Such  will  justify  the  use  of  a  foundation 
of  a  more  temporary  character  than  could  be  tolerated  for  per- 


Fig.  59. 


92 


RAILROAD  ENGINEERING 


manent  work.  When  time  is  important  and  the  ground  soft,  piles 
are  sometimes  driven  and  sawed  off  a  little  above  the  ground. 
They  are  so  placed  that  a  pile  comes  as  nearly  as  possible  under 
each  post  of  the  trestle.  Of  course,  such  foundations  must  be  con- 
sidered as  very  temporary  in  character,  as  they  will  speedily  decay 
to  such  an  extent  as  to  render  them  unsafe.  Locust  or  chestnut 
are  preferable  for  this  purpose. 


''''%KXNX  X  XXXX  Xt 

<XXXK~^)<y<K-)Pf^"" 

^^^M2^)^XXXXX) 

^XXXXaX^/t 

"^^^S^Xaa) 

\2qIxJ^^ 

-"yy^^JL^/^ 

w 

Fig.  60. 


jj^ 


Another  form  which  is  even  easier  to  construct,  but  which  is, 
if  possible,  still  more  subject  to  decay,  is  the  "mud-sill"  founda- 
tion. The  sill  of  the  trestle  is  set  on  a  number  of  timbers  placed 
transverse  to  the  sill,  the  timbers  being  about  12X12  in.  X  6  ft. 
If  the  ground  is  very  soft  even  these  timbers  may  be  set  on  two  or 
more  long  timbers,  laid  parallel  to  the  sill,  as  shown  by  the  dotted 
lines  in  Fig.  62. 

When  the  trestle  is  intended  as  a  permanent  structure,  and 
especially  when  it  is  intended  to  ultimately  replace  it  with  a  steel 

viaduct,  a  stone  foundation 
may  be  used.  If  built  of 
rough  rubble  the  wall  should 
be  about  4  feet  thick.  If 
the  masonry  was  of  a  better 
m7T7m77?Tn777777r^7^r^^^     ^.lass  the  wall  need  not  be  so 

thick,  but  the  cost  would  be 
Fig- 61.  about  the  same.     Usually  a 

single  continuous  wall  would 
be  built,  but  if  the  trestle  is  very  high  the  usual  batter  adopted  for 
the  side  posts  will  make  the  sill  very  long.  With  some  designs  of 
trestles,  depending,  however,  on  the  plan  of  the  posts,  it  is  per- 
missible to  save  some  masonry  by  omitting  portions  of  the  wall 
between  the  center  and  the  ends. 


/[ 


H 


RAILROAD  ENGINEERING 


93 


a. 


hH4 


H 


SILL 


88.  Abutments.  At  each  end  of  a  trestle  the  natural  sur- 
face usually  approaches  the  grade  line  by  a  slope.  If  stone  founda- 
tions were  built  for  the  bents,  then 
stone  abutments  would  be  built 
which  would  act  as  a  retaining  wall 
for  the  last  few  feet  of  rise  and 
which  would  support  the  last  string- 
ers. When  piles  are  used  an  abut- 
ment such  as  indicated  in  Fig.  63 
is  used.  When  no  piling  is  used, 
an  abutment  may  be  made  in  the 
form  of  crib  work.  Sometimes  one 
end  of  the  last  line  of  stringers  is 
merely  buried  in  the  earth  or  is 
supported  on  a  "mud  sill."  Of  course,  all  of  these  latter  methods 
should  be  considered  as  temporary.  The  danger  in  them  lies  in 
the  chance  of  these  places  being  neglected  and  the  decay  unnoticed 
until  the  decayed  timber  suddenly  gives  way  and  a  costly  accident 
is  the  result. 


r 



... 

] 

a»LL                      .1 

r 



— 

4 

Fig.  62. 


TRESTLE  FLOOR  SYSTEMS. 

89.  Stringers.  The  design  of  stringers  depends  somewhat 
on  the  cost  and  practicality  of  obtaining  timbers  of  the  length 
and  thickness  that  theory  would  call  for  as  the  most  economical 

size.  Sound  timber  of  the 
required  length,  and  more 
than  16  or  17  inches  in 
tTiickness,  is  scarce  and  cor- 
respondingly costly.  The 
required  transverse  strength 
for  stringers  is,  therefore, 
obtained  by  taking  as  large 
pieces  as  may  be  readily 
obtained,  setting  them  on 
Fig.  63.  edge  or  with   the    largest 

cross -sectional  dimension 
vertical,  and  then  bolting  two  or  more  of  them  together  side  by 
side.    Two  timbers,  each  8X16  in.,  bolted  together  side  by  side 


94 


RAILROAD  ENGINEERING 


with  the  16  in.  dimension  vertical,  are  practically  as  strong  as  a 
16X16  in.  timber,  and  are  very  much  easier  to  obtain  in  a  somid 
condition.  These  stringers  should  preferably  extend  over  two  spans, 
the  lines  "breaking  joints."  This  requires  pieces  from  20  to  32  ft. 
in  length.  The  pieces  of  each  line  should  be  separated  by  ''separat- 
ors," which  are  sometimes  cast-iron  spools,  1  or  2  in.  long,  which 
are  strung  on  the  bolts,  or  are  sometimes  made  of  pieces  of  plank 
about  6  feet  long.  Bolts  are  run  through  the  stringers  and  sep- 
arators. The  plank  separators  thus  serve  to  tie  the  consecutive 
stringers  together.  The  chief  object  of  the  separators  is  to  permit 
air  to  circulate  freely  around  the  timbers.  Placing  the  rough 
sawed  timbers  side  by  side  would  allow  water  to  soak  in  and  be 
retained,  so  that  decay  would  be  very  rapid.  The  design  of 
stringers  is  susceptible  of  exact  calculation  for  the  transverse 
strength  required,  but  as  this  is  a  direct  application  of  the  subject 
of  "Strength  of  Materials,"  the  method  of  design  will  not  be 
elaborated  here,  except  to  call  attention  to  the  fact  that  the 
stringers  must  be  designed  to  withstand  not  only  transverse 
strains,  but  also  shearing  and  crushing  across  the  grain  w^here  the 
stringer  rests  on  the  cap.  A  very  high  and  narrow  stringer  might 
have  sufficient  transverse  strength,  but  might  be  so  narrow  that  it 
would  fail  by  shearing  along  the  neutral  axis.  The  same  stringer 
might  also  have  such  a  small  area  where  it  rests  on  the  cap  that 
the  safe  limit  of  crushing  across  the  grain  might  be  exceeded.  The 
safe  values  to  be  used  with  various  kinds  of  wood  for  these  various 
stresses  may  be  found  in  many  handbooks.  The  following  dimen- 
sions have  the  approval  of  very  extensive  practice : 


Clear  Span. 

Number  of  pieces 
under  each  rail. 

Width. 

Depth. 

10  feet. 
12     " 
14     " 

2 
2 
3 

8  inches. 
10       " 
10       " 

16  inches. 
16       " 
16       " 

90.  Corbels,  A  corbel  ia  a  trestle  is  the  name  applied  to  a 
timber  placed  on  the  cap  of  the  trestle,  bent  and  on  which  the 
stringers  rest,  Fig.  64.  The  argument  in  favor  of  their  use  seems  to 
be  that  they  greatly  increase  the  area  of  pressure  on  the  seat  of  the 
stringer.    They  can  also  be  utilized  to  bind  together  two  abutting 


RAILROAD  ENGINEERING 


95 


stringers.  But  although  the  crushing  of  the  end  of  the  stringer 
may  be  prevented,  the  area  of  contact  between  the  corbel  and  the 
cap  must  be   considered,   to  determine   whether   crushing  might 


;&THIKGtR 


5-4- 


CORBEL 


\aAM 


4^ 


U 


Fig.  64. 

occur  there.    There  is  great  diversity  of  opinion  regarding  their 
use.    Many  standard  designs  do  not  use  them. 

91.  Guard  Rails.  These  are  timbers  varying  in  size  from 
5  X  8  in.  to  8  X  8  in.  which  are  placed  near  the  ends  of  the  ties. 
They  are  usually  notched  about  1  inch  at  each  tie  so  that  they 
really  form  tie  spacers  and  thus  prevent  the  ties  from  becoming 


Fig.  65. 

displaced  if  a  car  becomes  derailed  on  the  trestle.  They  should 
be  bolted  to  the  ties  at  every  third  or  fourth  tie.  There  are  vari- 
ous methods  of  jointing  the  ends  of  abutting  pieces.  The  method 
shown  in  Fig.  65,  is  perhaps  as  good  as  any. 


OOTEH  GUARD  RAIU 
INNER   GUARD  RAiu 


STRINGERS 


Fig.  66. 

The  name  guard  rail  is  also  appUed  to  the  inner  guards  which 
are  placed  about  10  in.  inside  of  each  rail,  Fig.  66.    These  are  usually 


96 


RAILROAD  ENGINEERING 


the  ordinary  T-rails  used  for  traction.  These  rails  are  rehed  on  to 
keep  the  cars  on  the  trestle  if  they  should  become  derailed.  If  a 
car  should  become  so  displaced  that  the  wheel  reached  the  outer 
wooden  guard  rail,  it  would  probably  catch  on  it,  slew  around  and 
jump  over.  Therefore  the  sole  function  of  the  outer  wooden  guard 
rail  is  to  keep  the  ties  spaced  and  in  place-. 

92.  Trestle  Ties.  Trestle  ties  are  always  made  of  sawed 
timber.  They  are  longer  than  ordinary  ties — usually  9  to  12  feet. 
The  depth  is  frequently  much  greater,  with  the  apparent  idea  that 
they  may  act  as  a  flooring  that  will  support  the  rolling  stock  if  it 
should  become  derailed.  For  a  similar  reason  the  spacing  is  made 
very  much  closer — generally  equal  to  or  less  than  the  width  of 
the  ties.  Sometimes  even  the  ties  are  notched  on  the  underside 
where  they  rest  on  the  stringers.     Some  plans  have  a  stringer  run 

under  each  guard  rail.  Then 
bolts  will  be  run  through 
the  stringer,  tie  and  guard 
rail  at  every  third  or  fourth 
tie.  If  the  ties  have  been 
notched  down  on  the  string- 
ers and  the  guard  rail  is 
notched  down  on  the  ties, 
then  these  bolts  will  tie  the 
whole  system  immovably 
together. 

93.  Super=Elevation  of 
the  Outer  Rail  on  Curves. 
Locating  a  curve  where  a 
trestle  is  also  necessary,  is 
in  general  very  objection- 
able, but  it  is  sometimes 
unavoidable.  The  objection 
lies  not  only  in  the  fact  that  a  very  considerable  force  is  required 
to  guide  the  train  in  its  circular  path,  but  the  force  is  variable, 
depending  on  the  variable  speed,  and  there  are  apt  to  be  oscillations 
of  unknown  force  which  will  still  further  rack  the  trestle.  Never- 
theless these  forces  must  be  provided  for  as  closely  as  possible. 
If  all  trains  moved  along  the  trestle  at  precisely  the  same  speed, 


Fig.  67. 


RAILROAD  ENGINEERING 


97 


1T~^ 


CAP 


the^  problem  would  be  comparatively  simple.  The  whole  floor 
system  could  be  designed  to  resist  the  thrust  due  to  the  forces  devel- 
oped at  that  speed.  But  since  the  speed  may  vary  dowTi  to  zero, 
and  the  train  start  from  rest  while  on  the  trestle,  which  of  itself 
will  introduce  new  strains, 
the  construction  which  is 
best  for  the  highest  speed 
is  not  the  best  when  the 
train  is  standing  on  the 
trestle,  or  when  it  is  start- 
ing, and  vice  versa.  A  few 
of  the  many  designs  which 
have  been  used  will  be 
illustrated,  together  with 
abrief  comment  on  the 
advantages  and  disadvan- 
tages of  each  design.  The 
required  super-elevation 
of  the  outer  rail  and  the 
method  of  computing 
it  will  be  discussed  in  the  chapter  on  track  work  and  track  laying. 
(a)  Inclining  floor  system  and  cap;  sill  horizontal;  outer  posts 
longer  J  Fig.  67.  The  construction  of  the  trestle  bents  is  more  com- 
plicated, but  that  of  the  floor 
system  is  simplified.  Since  the 
stringers  do  not  stand  vertically 
there  is  a  tendency  for  them  to 
twist  when  the  train  is  sta- 
tionary. 

(h)     Placing   wedges    under 
the  ties  at  each  tie.     Two  or  more 
wedges  are  required  for  each  tie. 
Each  wedge   is   bolted   by  two 
bolts.     The  number  of  pieces  is 
very  great,  but  there  is  the  advan- 
tage that  the  ties  are  not  notched  or  weakened  in  any  way.     If  for 
any  reason  a  different  super-elevation  is  desired  the  wedges  are  all 
that  need  be  changed. 


Fig.  68. 


Fig.  69. 


98 


RAILROAD  ENGINEERING 


(c)  Placing  a  wedge  under  the  outer  rail  at  each  tie,  Fig.  68. 
This  is  similar  to  the  last  method,  but  requires  fewer  pieces.  If 
the  super-elevation  is  slight,  either  very  long  spikes  must  be  used 
or  lag  screws  may  be  used  which  will  run  through  the  wedges  into 
the  ties.  For  a  greater  super-elevation  the  wedge  must  be  fas- 
tened, as  shown  in  the  illustration. 

(d)  Corbels  of  varying  height,  Fig.  69.  The  whole  floor  system 
is  tipped  as  in  a,  but  the  trestle  bent  is  as  usual,  with  cap  and 
sill  horizontal.  In  all  such  cases,  where  the  axis  of  the  post  is 
vertical,  the  lateral  bracing  of  the  bent  should  be  made  extra 
heavy.  It  should  be  especially  noted  whether  the  center  of  pressure 
under  extreme  conditions  reaches  the  sill  too  near  the  outer  end  of 

the  sill. 

(e)  Tipping  the  whole  bent  on  its 
foundation.  The  advantages  and  dis- 
advantages of  the  method  under  some 
conditions  are  obvious. 

(/)  Notching  the  cap,  Fig.  70.  The 
method  is  mentioned  on  account  of  its 
frequent  use,  but  the  disadvantages  are 
very  great.  The  cap  is  weakened  by  the 
notching.  Either  the  stringer  or  the  tie 
must  be  notched  at  each  tie.  Usually  the 
tie  would  be  hopelessly  weakened  if  it  were  notched  sufficiently, 
and,  therefore,  the  stringers  must  be  notched.  The  method  is  costly 
in  construction  and  objectionable  when  made.  The  above  methods 
are  types  of  a  great  variety  of  plans  of  construction  which  have 
been  suggested  and  tried. 

94.  Protection  Against  Fire.  One  of  the  strongest  objec- 
tions against  the  use  of  trestles  is  the  danger  from  fire.  Sparks 
from  the  locomotive  or  wayside  fires  kindled  by  tramps  and  others 
may  destroy  them,  or,  what  is  still  more  dangerous,  may  slowly 
eat  into  the  timbers  until  they  are  weakened  beyond  the  danger 
line,  and  yet,  because  the  effect  of  the  fire  is  not  apparent  to  a 
careless  inspection,  it  may  result  in  an  appalling  accident.  The 
danger  from  falling  coals  from  the  locomotive  firebox  is  largely 
obviated  by  constructing  a  solid  floor  or  trough  on  the  stringers, 
the  trough  being  filled  with  ballast  and  the  ties  set  in  the  ballast 


Fig.  70. 


108 


Af-'jlf^-A^V^ 


4;  _  f^iJJ — i i — 'ul^-eisi  //o' 


O'xB'x/z'o^ 


f^ote :  Smry  Bracing  io  be    ^ 

omifttc^  on  Pile  Bents        ^ 

under  4-  ft.  fiig/t.  "6 


yTies  e'e't iz'o' Iz'Cfrj.  Spiked 
0  Jack  Strinaers  mfh  one 
'■'x  lO'eoat  Spikes  left  pro- 


yecfingr  ^"abore  tie.        pr-i 


Type  of   Pile  Bent. 

Type  of  Framed  Bent  16' 

jXjyfcrcA^  stringer  Sir /6t2^'^\  |7]_ 


''Quarc/  Rail,  0x8 


Plan. 


n      Qlrt,  6TrS\ 


Guard  Rail  Splice. 
^  ..12"— -^^-IZ-"-  -X-  —Id"-  -  ■  ->i 


ff988.^    kV^-VF-V .z(5'-----*^---/S--->¥--/S-  ->f ^J— -^--/fL? 


T-R.4-74- 

Detail  of  Stringer  Joint. 
r         0         I"         t         3' 


T  //     %-B^lt  ,„    Jl 

Section  Through  Floor. 


Fig    71.     Standard  Framed  Trestle  as  led 


3x/0x/80 


Boat  Sp!/f»,  fjr ' ' 


Notes   on  Tre 

stie    Bents.                                         1 

Height  of  Bent 

Length  of  Pjsts 

5///S 

^^ 

ofSnc 
I8ff. 

ZOft 

es  ana 

22ff. 

^ 

^ 

lift 

16  ff. 

Wff 

2 

18  . 

20  » 

2 

?l  . 

20  » 

20  . 

2 

?J  , 

? 

25. 

22. 

2 

27. 

22. 

2 

29. 

28 . 

?4. 

2 

4- 

2 

31. 

30. 

?4. 

2 

4 

2 

33. 

32. 

24, 

2 

[^_ 

■^ 

RAILROAD  ENGINEERING  99 

as  usual.  Another  method  is  to  cover  the  stringers  and  caps  with 
sheet  metal.  A  very  long  trestle  generally  deserves  the  protection 
of  a  special  watchman  or  track  walker.  ]\Ieans  for  fighting  a  fire 
when  discovered  are  provided  by  reservoirs  of  water,  made  perhaps 
from  halves  of  oil  barrels,  which  are  placed  on  the  trestle  at  inter- 
vals of  300  feet.  Three  or  four  ties  are  made  about  4  feet  longer  than 
the  usual  length.  These  form  the  floor  of  a  platform,  which,  when 
provided  with  a  railing,  forms  not  only  a  place  for  the  barrel,  but 
also  a  refuge  bay  for  the  track  walker,  who  may  be  on  the  trestle 
when  a  train  is  passing. 

95.  Choice  of  Timber.  When  a  railroad  is  being  run 
through  a  virgin  country  where  timber  is  plentiful  and  there  is 
frequent  occasion  for  trestles,  it  pays  to  take  a  portable  sawmill 
to  the  spot  and  saw  the  timber  as  required.  Under  such  condi- 
tions any  one  of  the  various  kinds  of  timber  which  are  ever  used 
for  building  purposes  will  answer.  If  necessary,  the  cross-sec- 
tions can  be  increased  to  correspond  with  the  reduced  strength  of 
a  weaker  wood.  But  when  the  wood  must  be  transported  a  con- 
siderable distance  and  it  is  practicable  to  choose  among  various 
kinds  of  w^ood,  the  selection  should  be  made  according  to  favorable 
qualities.  Ties  and  guard  rails  should,  if  possible,  be  of  oak. 
Stringers  should  be  made  of  oak  or  pine.  Since  one  of  the  chief 
uses  of  corbels  is  to  relieve  a  dangerous  pressure  across  the  grain 
they  should  be  made  of  the  hardest  wood  obtainable,  such  as  oak, 
hickory  or  ash.  The  bents  of  a  framed  trestle  may  be  made  of 
almost  anything,  but  oak,  pine  or  fir  are  preferable  when  obtain- 
able. If  the  sills  are  liable  to  become  buried  somewhat  in  the 
ground  so  that  rain  will  not  readily  be  shed,  then  some  wood  like 
cedar,  which  is  very  long-lived  under  ground,  might  be  preferable, 
but  the  strength  as  posts  will  be  somewhat  less  than  that  of  oak. 
The  chemical  treatment  of  timber  for  trestles  is  seldom  used,  except 
for  trestles  which  are  partly  immersed  in  water  where  the  teredo 
navalis  is  found.  Trestles  are  usually  considered  to  be  so  cheap 
and  temporary  that  conditions  which  would  justify  the  additional 
expense  of  chemical  treatment  would  also  justify  the  immediate 
construction  of  a  permanent  structure  of  steel  or  stone. 

On  the  folding  plate.  Fig.  71,  is  shown  the  standard  plans 
for  a  framed  trestle  as  adopted  by  the  Great  Northern  Railroad. 


100 


RAILROAD  ENGINEERING 


Many  of  the  details  shown  will  verify  those  already  mentioned, 
while  in  other  cases  the  variations  in  detail  represent  practice  equally 
good.     The  plate  is  well  worthy  of  a  long  and  close  study. 

CULVERTS. 

96.  Pipe  Culverts.  The  scarcity  of  stone  suitable  for  mak- 
ing a  "box"  or  "arch"  culvert  has  led  to  the  adoption  for  many 
localities  of  pipe  culverts,  the  pipes  being  made  of  tile  or  iron,  Fig. 
72.  Pipes  have  several  very  great  advantages.  Their  form  is 
hydraulically  better  than  any  rectangular  form  and  the  surface  is 


Note!  Where  character 
of  soil  will  permit, 
this  concrete  need 
not  be  used 


Fig.  72.     Pipe  Culvert. 

usually  very  much  better  than  an  ordinary  masonry  culvert.  There- 
fore they  will  discharge  a  far  greater  volume  of  water  than  a  box 
culvert  of  equal  area.  They  are  very  easily  placed  without  skilled 
labor.  Sometimes  they  are  set  inside  of  a  wooden  box  culvert 
temporarily  placed  during  the  construction  of  the  road.  When 
one  pipe  of  the  size  which  it  is  desired  to  use  has  insufficient  area 
two  or  more  pipes  may  be  used  side  by  side.  This  feature  is  of 
special  value  when  the  head  room  between  the  bed  of  the  stream 
and  the  grade  line  is  limited.  Iron  pipe  usually  has  such  inherent 
strength  that  there  is  little  need  for  special  care  in  securing  a  foun- 
dation for  the  pipe.  A  little  block  of  concrete  at  each  joint  is  suffi- 
cient for  ordinary  cases,  but  tile  pipe  requires  a  secure  foundation. 


RAILROAD  ENGINEERING 


101 


The  danger  to  the  pipe  does  not  lie  so  much  in  the  mere 
static  pressure  of  the  earthwork  embankment  above  it  as  in  the 
effect  of  settlement  of  a  "green'*  embankment.  If  the  pipe  is 
laid  on  the  natural  soil,  which  might  be  tolerated  if  it  is  very  firm, 
a  bed  should  be  carefully  scooped  out  so  as  to  fit  the  pipe  as  closely 
as  possible.  A  better  plan  is  to  place  a  thick  layer  of  broken  stone 
or  brickbats  and  ram  them  to  the  proper  form  as  a  bed  for  the 
pipe.  A  still  better  plan  is  to  place  a  layer  of  concrete  under  the 
whole  length  of  the  pipe.  The  required  slope  of  the  pipe  depends 
somewhat  on  the  accuracy  of  the  laying  and  on  the  permanency 
of  the  work.  A  slope  of  1  per  cent  is  ample,  provided  the  grade 
be  made  and  maintained  uniform,  but  the  effect  of  settlement  may 
be  to  change  such  a  grade  to  a  negative  grade,  which  would  pre- 
vent the  water  from  being  carried  off.     Some  standard  plans  there- 


Fig.  73. 


Old-Rail  Culverts. 


Fig.  74. 


fore  require  a  grade  as  steep  as  1  in  20.  At  each  end  of  the  pipe 
there  should  be  a  substantial  head  wall  of  masonry.  Some  stand- 
ard plans  make  this  wall  very  large  and  heavy  with  elaborate  wing 
walls.  These  are  justifiable  on  the  grounds  of  preventing  the 
water  at  the  upper  end  from  scouring  around  the  ends  of  the  head 
wall  or  of  preventing  the  outflowing  water  from  scouring  away 
the  bed  of  the  stream  and  thus  undermining  the  lower  head  wall. 
An  iron  pipe  can  be  used  if  necessary  very  close  to  the  ties, 
but  a  tile  pipe  should  have  a  cushion  of  at  least  three  feet  between 
the  tile  and  the  ties.  The  joints  in  the  pipe  should  always  be 
caulked.  Clay  puddle  is  much  used  for  this  purpose  and  when  it 
is  of  good  quality  and  the  work  well  done,  the  results  are  satis- 
factory, but  if  clay  puddle  cannot  be  obtained  it  is  better  to  use 
hydraulic  cement.  The  cost  of  the  cement  is  an  insignificant  item 
considering  the  value  of  the  result. 


102  RAILROAD  ENGINEERING 

97.  01d=Rail  Culverts.  These  have  an  especial  value  when 
the  head  room  between  the  bed  of  the  stream  and  the  rails  is  small, 
and  when  it  is  also  necessary  to  provide  for  a  considerable  flow  of 
water.  The  old  rails,  even  when  worn  out  as  rails,  still  have  a 
considerable  strength  as  girders  and  a  continuous  layer  of  them 
is  amply  strong  enough  to  carry  the  roadbed  and  the  traffic  over 
a  six-foot  opening.  The  rails  may  be  bound  together  by  means 
of  tie  rods  run  through  the  webs  of  the  rails,  but  they  may  also 
be  confined  by  stones  at  each  end  of  the  seat  course  on  each  abut- 
ment. Figs.  73  and  74. 

Another  advantage  of  this  form  of  opening,  over  the  com- 
mon plan  of  supporting  the  ties  on  stringers  or  steel  girders,  is 
that  in  this  plan  the  ballasted  roadbed  is  continuous.  This  is  a 
great  advantage  both  from  the  standpoint  of  smooth  riding  and  of 
safety. 

98.  Cattle  Passes.  When  an  embankment  crosses  a  farm, 
cutting  it  in  two,  it  becomes  necessary  for  the  road  to  provide  a 
passage  way  through  the  embankment  for  the  use  of  cattle  and 
farm  wagons.  The  cost  of  such  a  structure  is  compensated  by  the 
relief  of  the  company  from  damages  due  to  the  cattle  crossing  the 
road  at  grade.  These  openings  are  sometimes  built  as  large  stone 
arch  culverts  or  as  old-rail  culverts,  especially  if  there  is  liable  to 
be  a  storm-water  flow  throrugh  them.  Another  method  is  to  set 
two  trestle  bents  at  the  requisite  distance  apart;  3-inch  planks  are 
set  behind  the  bents  to  hold  the  earthwork  embankment;  the 
stringers  are  notched  down  so  as  to  take  up  the  thrust  of  the  embank- 
ment. This  method  naturally  applies  to  embankments  which  are 
from  about  8  to  15  feet  in  height.  The  disadvantage  incident  to 
all  wooden  structures  set  in  earth  also  applies  here.  There  is  also 
the  disadvantage  of  a  break  in  the  continuity  of  the  ballasted  road- 
bed, as  well  as  the  danger  due  to  an  accident  from  fire  destroying 
or  weakening  the  structure.  When  the  head  room  is  limited,  a 
first-class  permanent  construction  can  best  be  obtained  by  the 
"old-rail"  method  or  something  similar. 


i^.„^;ii^ 


RAILROAD  ENGINEERING. 

PART  II. 


MISCELLANEOUS  STRUCTURES. 

99.  Water  Supply.  The  railroads  of  the  country  spent  in 
1910  over  $13,000,000  in  supplying  water  to  their  locomotives. 
Part  of  this  expense  is  due  to  the  fact  that  a  bad  quality  of  water 
is  so  injurious  to  a  locomotive  boiler  (as  well  as  rendering  it  diffi- 
cult for  the  boiler  to  steam  properly)  that  the  added  expense  of 
procuring  a  suitable  supply  of  naturally  pure  water  or  of  purify- 
ing an  impure  supply  is  amply  justified.  A  natural  water  supply 
is  always  more  or  less  charged  with  calcium  and  magnesium  car- 
bonates and  sulphates  in  addition  to  impurities  of  almost  any 
nature  which  come  in  as  the  refuse  from  factories,  etc.  Some  of 
these  impurities  are  comparatively  harmless,  especially  if  the 
quantity  is  not  large.  But  the  evaporation  of  the  water  precipi- 
tates the  calcium  and  magnesium,  which  form  deposits  on  the 
surface  of  the  boiler. 

These  deposits  are  injurious  in  two  ways.  In  the  first  place 
the  transfer  of  heat  from  the  fire  to  the  water  is  less  free  and 
there  is  thus  a  waste  of  energy,  and  in  the  next  place  the  metal 
becomes  overheated  and  perhaps  "burned."  The  safety  of  the 
metal  of  a  boiler  depends  on  the  free  transfer  of  the  intense  heat 
of  the  fire  to  the  comparatively  low  heat  of  the  water  or  steam. 
The  prevention  of  these  deposits  may  be  accomplished  in  one  (or 
both)  of  two  ways;  the  frequent  cleaning  of  the  boilers  through 
the  manholes  and  handholes  provided  for  the  purpose,  and  by  the 
more  or  less  perfect  purification  of  the  water  before  it  enters  the 
boiler. 

The  location  of  the  water  stations  must  be  at  such  places  and 
intervals  as  the  service  demands.  There  must  always  be  a  supply 
at  the  extremities  of  each  division  and  usually  at  intervals  of  15 
to  20  miles  between.  Of  course  these  intervals  are  varied  accord- 
ing to  the  location  of  convenient  sources  of  supply.     The  frequent 


104  RAILROAD  ENGINEERING 

erection  of  municipal  plants  for  water  supply  even  in  small  places 
has  led  to  the  utilization  of  such  plants,  since  a  suitable  supply 
for  domestic  use  is  usually  satisfactory  for  boiler  use,  and  since  a 
reasonable  charge  to  such  a  large  consumer  would  generally  be  far 
less  than  the  cost  of  maintaining  a  separate  plant.  In  default  of 
such  supplies,  a  convenient  intersecting  stream,  especially  when 
combined  with  an  existing  but  perhaps  abandoned  mill  dam  which 
will  form  a  convenient  storage  reservoir,  may  be  utilized.  If  the 
stream  passes  through  a  limestone  region,  the  water  may  become 
so  thoroughly  impregnated  with  calcium  compounds  that  a  purify- 
ing plant  will  become  a  necessity  and  then  there  may  arise  the 
question  of  a  choice  between  a  conveniently  located  station  with  a 
necessary  purifying  plant  and  a  less  convenient  location  but  a  nat- 
ural supply  of  purer  water. 

The  chemical  purification  of  water  for  railroad  purposes  has 
become  a  specialty  and  must  be  studied  as  such.  Of  course  no 
attempt  is  made  to  produce  chemically  pure  water  as  that  would 
be  unnecessarily  costly.  The  reagents  chiefly  employed  are  quick- 
lime  and  sodium  carbonate.  The  lime  precipitates  the  bicarbon- 
ate of  lime  and  magnesia  in  the  water.  Sodium  carbonate  gives, 
by  double  decomposition  in  the  presence  of  sulphate  of  lime, 
carbonate  of  lime,  which  precipitates,  and  soluble  sulphate  of  soda, 
which  is  non-incrustant.  The  precipitates  settle  to  the  bottom  of 
the  tank  and  are  drawn  off  while  the  purified  water  is  drawn  from 
the  upper  portion  of  the  tank.  Such  purification  may  be  accom- 
plished for  a  few  cents  per  thousand  gallons.  Still  another  method 
of  preventing  incrustation  in  the  boiler  is  to  introduce  directly  into 
the  water  tank  a  "non-incrustant"  which,  as  its  name  implies,  will 
so  change  the  composition  of  the  impurities  that  they  will  settle 
harmlessly  and  may  be  readily  blown  out. 

Pumping,  Except  when  water  is  obtained  from  a  municipal 
water  supply  it  must  be  pumped  into  a  tank  or  reservoir  which  is 
usually  placed  with  its  bottom  12  to  15  feet  above  the  rails.  The 
pumping  may  be  done  with  a  wind  mill,  which  is  very  cheap  but 
unreliable,  or  by  an  ordinary  steam  pump  operated  by  a  boiler  fed 
with  coal,  or  by  a  gasoline  engine.  The  last  method  is  becoming 
very  popular,  as  the  pumps  require  but  little  attention  and  the  cost 
of  operating  them  has  been  found  to  be  as  low  as  one-third  or  even 


RAILROAD  ENGINEERING 


105 


one-fourth  of  the  cost  of  steam  pumping.  And  this  is  true  in 
spite  of  the  fact  that  a  railroad  can  usually  deliver  slack  coal  or 
screenings  at  a  pump  house  alone  the  line  of  the  road  at  a  cost  that 
may  not  exceed  30  cents  per  ton.  The  cost  of  pumping  to  a  track 
tank  will  usually  run  at  from  2  cents  to  6  cents  per  1,000  gallons. 

Tanks.  The  construction  of  the  piping  from  a  tank  and  even 
of  the  tanks  themselves  has  become  a  specialty  by  manufacturing 
firms  who  can  make  and  sell 
them  much  cheaper  than  may 
be  done  by  any  ''home-made" 
method,  and,  therefore,  the 
details  of  manufacture  need 
not  be  here  discussed.  The 
tank  must  be  so  placed  that 
its  nearest  face  is  about  8 
feet  6  inches  from  the  track 
center.  When  one  tank  is  to 
serve  several  tracks  or  when 
the  supply  is  taken  from  a 
city  waterworks,  a  "  stand- 
pipe"  is  necessary.  This 
consists  essentially  of  an  up- 
right pipe  which  stands 
about  14  feet  above  the 
ground  where  it  has  a  hori- 
zontal arm  about  7  feet  long. 
This  elbow  may  be  turned 
so  that  the  arm  is  either  par- 
allel or  perpendicular  to  the 
track.  As  shown  in  Fig.  75, 
the  valve  mechanism  is  bur- 
ied underground  and  the  roof 
of  the  pit  is  protected  so  that  freezing  shall  be  obviated. 

Track  Tanks.  The  demands  for  high  speed  require  that  long 
runs  shall  be  made  without  a  stop  even  for  water.  Very  long 
runs  can  only  be  made  by  taking  on  water  while  in  motion  from  a 
track  tank.  These  have  a  length  of  1,200  to  1,500  feet  and  must 
be  laid  on  a  stretch  of  perfectly  level  track.     A  large  item  in  the 


Fig.  75.    Automatic  Standpipe. 


106  RAILROAD  ENGINEERING 

expense  of  installing  such  a  plant  is  the  cost  of  the  re-grading 
which  is  usually  necessary  to  make  the  track  perfectly  level.  On 
the  ties  and  midway  between  the  rails  is  a  tank  about  19  inches 
wide,  6  inches  deep  and  as  long  as  desired.  This  trough  will  be 
made  of  ^-inch  steel  plate,  stiffened  and  reinforced  with  angle 
bars.  Such  tanks  can  only  be  used  by  engines  which  are  provided 
with  a  scoop  on  the  tender  which  is  lowered  at  the  proper  time. 
The  high  speed  causes  the  water  to  rush  into  the  scoop  with  such 
velocity  that  it  is  easily  carried  to  the  top  of  the  leader  pipe  and 
over  into  the  tender  tank.  An  inclined  plane  at  each  end  of  the 
trough  automatically  raises  the  scoop  and  when  raised  it  is  auto- 
matically caught  and  held  so  that  there  is  no  danger  that  the  scoop 
shall  catch  in  anything  on  the  track.  To  prevent  the  water  from 
freezing  in  the  winter,  steam  jets  should  be  blown  into  the  water 
at  every  40  to  50  feet  of  its  length.  The  steam  required  for  this 
may  be  many  times  as  great  as  the  steam  required  for  pumping. 
The  cost  of  such  an  installation  will  be  upwards  of  $10,000  and 
the  annual  expense  about  $1,500.  Of  course  these  figures  will 
vary  with  the  circumstances. 

loo.  Turntables.  The  turntable  proper  is  an  example  in 
,  structural  engineering  which  is  now  almost  universally  made  of 
structural  steel  in  shops  which  make  such  .work  their  specialty. 
Therefore  no  discussion  will  be  given  of  the  table.  But  the  table 
must  be  supported  on  a  pivot  which  must  have  an  adequate  foun- 
dation which  must  be  able  to  support  a  load  of  perhaps  200  tons. 
The  table  revolves  in  ti  pit  which  is  say  75  feet  in  diameter  and 
which  must  have  a  retaining  wall  about  it.  Immediately  inside 
of  this  wall  is  a  circular  track  on  which  rollers  on  the  under  side 
of  the  turntable  may  run  if  the  load  is  eccentric.  Since  this  load 
on  the  rail  may  be  large  it  must  have  an  adequate  support. 

If  the  turntlable  must  be  located  on  what  is  originally  sloping 
ground,  the  masonry  may  need  to  be  quite  deep  and  heavy,  sincG 
the  foundation  for  the  pivot  should  be  especially  firm.  If  the 
subsoil  is  not  self -draining,  it  should  be  thoroughly  drained  by  a 
thorough  sub-drainage  and  the  pit  should  be  drained  by  a  pipe 
leading  to  a  suitable  outfall.  A  turntable  is  usually  located  as  an 
adjunct  to  a  roundhouse,  but  in  any  case  the  location  should  be 
made  so  that  the  switching  that  must  be  done  before  and  after 


RAILROAD  ENGINEERING 


107 


Bucket  towcr 


fiUTOMATlC 
£LCCrR/C    HOIST 


Fig. 


300-Ton  Reinforced  Concrete  Locomotive  Coaling  Plant,  Provided  with  "Duplex' 
Shallow  Pit  Loader. 
Courtesy  of  Roberts  and  Schae/er  Company,  Chicago 


108  RAILROAD  ENGINEERING 

using  the  table  shall  be  made  a  miniiiiiiin.  The  location  of  the  turn- 
table in  the  yard  is  an  item  in  the  subject  of  Yards  and  Terminals. 
loi.  Coaling  Stations.  The  cost  of  removing  ashes  from 
the  ashpan  of  a  locomotive  to  a  suitable  dumping  ground  and  of 
supplying  the  tender  with  coal  may  amount  to  a  very  considerable 
item  unless  special  facilities  are  devised  for  doing  the  work  cheaply 
as  well  as  rapidly.  Such  facilities  are  especially  necessary  when 
the  number  of  locomotives  to  be  taken  care  of  is  very  great.  As 
will  be  seen  from  the  vertical  section  of  a  Roberts  and  Schaefer 
concrete  coal  loader,  Fig.  76,  the  coal  car  is  placed  over  the  12-foot 


Fig.  78.     Electrically  Operated  2000-Ton  Coaling  Station 

Fourteen  engines  can  be  supplied  simultaneously  with  coal,  sand,  and  water. 

Courtesy  of  Link-Belt  Company,  Chicago 

pit,  a  hopper  receiving  the  coal  from  the  car  and  a  traveling  loader 
conveying  it  to  the  bucket  hoist.  By  means  of  the  hoist  the 
coal  is  carried  to  the  top  of  the  tower  and  automatically  dumped 
into  the  storage  bins.  In  Fig.  77  is  shown  the  plan  view  of  the 
bucket  pit. 

Another  concrete  coaling  station  built  by  the  Link-Belt  Com- 
pany is  shown  in  Fig.  78.  This  has  a  capacity  of  2,000  tons  of  coal 
and  is  also  provided  with  sand  bins  and  facilities  for  taking  care  of 
the  cinders. 

102.  Engine  Houses.  On  very  small  roads,  where  the  num- 
ber of  engines  to  be  housed  at  any  one  place  will  never  exceed  five 


RAILROAD  ENGINEERING  109 

or  six,  a  rectangular  engine  house  with  two  or  three  parallel  tracks 
is  the  cheapest  form  of  construction.  But  as  the  number  of 
engines  to  be  provided  for  increases,  and  as  space  grows  more 
valuable,  the  "roundhouse"  is  preferable.  Considering  the  space, 
tracks  and  switches  required  to  run  a  large  number  of  tracks  into 
a  rectangular  house,  the  roundhouse  will  accommodate  more 
engines  in  proportion  to  the  space  required.  A  turntable  is  a 
necessary  feature  of  a  roundhouse,  but  since  a  turntable  would 
naturally  be  located  at  any  point  on  a  road  where  an  engine  house 
was  required  the  cost  of  the  turntable  should  not  be  considered 
as  an  integral  part  of  the  cost  of  the  roundhouse. 

Engine  houses  are  used  for  the  minor  repairs  which  contin- 
ually form  a  part  of  the  maintenance  of  any  locomotive.  There- 
fore a  portion  of  the  tracks  should  be  provided  with  "pits"  or 
spaces  between  the  rails  in  which  work  may  be  done  under  the 
engine.  The  outer  walls  are  preferably  constructed  of  masonry, 
although  wooden  structures  are  not  uncommon  on  cheaper  roads. 
The  roof  framing  should  preferably  be  of  wood,  as  iron  trusses 
deteriorate  very  fast  under  the  action  of  the  gases  of  combustion 
from  the  engines.  The  effect  of  this  is  prevented  as  far  as  possi- 
ble by  "  smoke  jacks,"  which  are  chimneys  suspended  from  the 
roof  so  that  they  are  immediately  above  the  engine  stack  when 
each  engine  is  placed  where  designed.  The  lower  part  of  this 
chimney  is  made  adjustable  so  that  it  may  come  down  closely  over 
the  stack.  The  smoke  jacks  are  variously  made  of  galvanized  iron 
(very  short  lived),  vitrified  pipe  (too  brittle),  cast  iron  (very  heavy), 
expanded  metal  and  concrete,  and  even  plain  wood  painted  with 
"fireproof"  paint.  The  floors  are  best  made  of  brick;  cinders 
are  cheap  but  objectionable,  wood  is  tolerable  but  lacks  durability, 
concrete  is  almost  an  extravagance.  Considering  that  the  larger 
roundhouses  may  contain  locomotives  worth  several  hundred 
thousand  dollars,  fire  protection  is  an  important  feature.  One 
means  to  this  end  is  the  use  of  rolling  steel  shutters  instead  of 
wooden  doors.  In  Fig.  79  is  shown  some  of  the  details  of  what 
may  be  considered  a  typical  roundhouse.  The  figure  will  illus- 
trate many  of  the  points  named  above. 

103.  Cattle  Guards.  The  prevalent  opinion  that  a  railroad 
company  is  responsible  for  the  death  or  injury  of  any  cattle  which 


RAILROAD  ENGINEERING 


111 


may  stray  on  its  right-of-way  requires  especial  precautions  that 
cattle,  straying  along  a  highway,  shall  not  turn  into  the  railroad 
right-of-way.     The  fundamental  idea  is  a  structure  which  is  not 


Fig.  80.    Climax  Cattle  Guard. 


an  obstruction  to  trains  but  over  which  cattle  will  not  pass.     The 
old  way  was  to  use  a  pit  about  two  feet  deep  and  four  feet  wide 


Fig,  81.    Sheffield  Cattle  Guard. 


across  which  the  rails  were  supported  on  wooden  stringers.     But 
this  form  makes  a  break  in  the  continuity  of  the  roadbed  and  is  a 


112  RAILROAD  ENGINEERING 

very  fruitful  source  of  accidents.     This  form  lias,  therefore,  been 
definitely  abandoned  for  "surface"  cattle  guards. 

Two  forms  of  these  are  illustrated  in  Figs.  80  and  81.  The 
variations  in  the  surface  adopted  are  multitudinous.  Usually  they 
are  made  of  iron,  sometimes  of  wood  and  sometimes  of  some  form 
of  tile  or  cement  which  is  not  subject  to  decay  or  rust.  Any  form 
must  have  in  addition  the  fences  extending  from  the  sides  of  the 
right-of-way  up  to  the  ends  of  the  ties.  These  fences  will  be 
"headed"  by  a  short  guard  fence,  as  shown  in  the  left  of  each  of 
the  figures,  which  will  prevent  cattle  from  stepping  over  the  end 
of  the  fence. 

TRACK  AND  TRACK  WORK  flATERIALS. 

104.  Ballast.  The  ideal  ballast  must  transfer  the  applied 
load  over  a  large  surface;  it  must  hold  the  ties  in  place  horizon- 
tally;  it  must  carry  off  the  rain  water  and  thereby  prevent  freez- 
ing up  in  winter;  it  must  be  such  that  the  ties  may  be  readily 
adjusted  to  the  true  grade  line  and  it  must  produce  an  elastic 
roadbed.  The  various  materials  used  for  ballast  fulfill  these  con- 
ditions in  variable  degrees  and  at  various  costs.  The  most  perfect 
and  costly  ballast  is  not  necessarily  the  best  for  a  light  traffic  road, 
but  on  the  other  hand  many  light  traffic  roads  are  increasing  their 
operating  expenses  (unconsciously)  in  a  vain  attempt  to  cut  them 
down  by  using  a  cheap  form  of  ballast  or  none  at  all.  The  prin- 
cipal kinds  used  will  be  stated  with  a  comment  on  each  one. 

Mud.  This  means  no  ballast  except  the  natural  soil.  Some- 
times the  natural  soil  is  sandy  or  gravelly  and  will  make  a  very 


Fig.  82.    Mud  BaUast. 

good  ballast  where  it  occurs,  but  no  matter  how  good  the  soil  may 
be  in  some  places,  such  a  quality  cannot  be  depended  on  to  be  con- 
tinuous throughout  the  line  or  even  approximately  so.  Consider- 
ing that  a  heavy  rain  will  in  one  day  spoil  the  results  of  weeks  of 
patient  "  surfacing  "  with  mud  ballast,  it  is  seldom  economical  to 
use  it  if  there  is  a  gravel  bed  or  other  sources  of  ballast  anywhere 


RAILROAD  ENGINEERING  113 

on  the  line  of  the  road.  If  it  must  be  used,  then  the  drainage 
should  be  exceptionally  perfect.  The  earth  should  be  crowned 
over  the  ties  in  the  center  and  the  ditches  on  each  side  should  be 
at  least  20  inches  bejow  the  base  of  the  ties.  This  will  facilitate 
the  flow  of  water  to  the  sides. 

Cinders.  The  advantages  are.  an  almost  perfect  drainage, 
ease  of  handling,  and  cheapness,  for,  after  the  road  is  in  opera- 
tion, their  use  is  but  the  utilization  of  a  waste  product.  The  chief 
disadvantage  lies  in  the  dust  produced  as  the  particles  are  ground 
up  by  use.  Incidentally,  a  light  traflic  road  would  require  a  long 
time  to  produce  enough  ashes  to  ballast  the  whole  road,  which 
would  imply  a  long  period  of  operation  with  no  ballast  at  all. 

Slag.  In  certain  places  such  ballast  is  very  cheaply  obtained 
as  a  waste  product,  it  being  given  away  for  the  hauling.  It  is  free 
from  dust  and  the  drainage  is  perfect. 

Shells.,  fine  coal^  etc.  These  are  only  used  when  their  prox- 
imity makes  them  especially  cheap.  They  become  dusty  in  dry 
weather  and  correspondingly  imperfect  in  their  drainage  qualities. 
They  soon  become  but  little  better  than  "  mud." 

Gravel.  A  large  proportion  of  the  railroad  mileage  of  the 
country  is  laid  with  gravel  ballast.  This  is  because  gravel  beds 
are  so  frequently  found  on  the  lines  of  roads,  from  which  the  gravel 


Fig.  83.    Gravel  Ballast. 

may  be  dug  with  a  steam  shovel,  loaded  on  to  cars  and  hauled  to  any 
desired  point  where  it  is  perhaps  unloaded  mechanically,  the  only 
strictly  hand  work  in  the  whole  operation  being  the  tamping  of  the 
ballast  in  the  track.  Such  methods  make  the  cost  per  cubic  yard 
very  small.  The  gravel  is  easily  handled  and  affords  almost  perfect 
drainage.  If  the  gravel  contains  very  fine  stones  or  dirt,  it  should 
be  screened  over  a  half-inch  screen  to  take  the  fine  stuff  out. 

Broken  Stone.  This  is  the  best  form  of  ballast  obtainable, 
and  usually  the  most  expensive.  Although  hand-broken  stone  is 
preferable,  the  cost  of  machine  crushed  stone  is  so  much  less  that 
it  is  almost  exclusively  used.     They  should  be  broken  so  that  they 


114  RAILROAD  ENGINEERING 

will  pass  through  a  1^-inch  or  2-inch  ring.  It  is  most  easily 
shoveled  with  forks,  and  this  method  has  the  additional  advantage 
that  the  finest  chips  and  dirt  will  be  screened  out.  Such  ballast  holds 
the  ties  more  firmly  than  any  other  form  and  hence  is  almost  an 
essential  for  roads  handling  a  great  and  heavy  traftic  at  high  speed. 
For  a  light  trafiic  road  running  few  trains  and  these  at  very  mod- 
erate speed,  the  use  of  rock  ballast  would  be  almost  a  useless  lux- 
ury unless  the  broken  stone  were  very  cheap  and  gravel  were 
expensive  or  unobtainable. 

Amount  required.  Good  practice  requires  a  depth  of  12 
inches  of  gravel  or  broken  stone  under  the  ties.  With  6-inch  X 
8 -inch  ties  spaced  24  inches  between  centers,  the  amount  between 
the  ties  will  be  equivalent  to  an  additional  depth  of  about  4  inches. 


If  the  ballast  has  an  average  w^dth  of  10  feet,  say  8  feet  at  the  top 
and  12  feet  at  the  bottom,  then  one  mile  of  track  will  contain  2,607 
cubic  yards.  Broken  stone  requires  a  little  more  than  this  since 
there  should  be  a  shoulder  of  ballast  on  the  ends  of  the  ties.  (See 
Fig.  84.) 

Method  of  laying.  When  ballast  is  laid  during  the  original 
construction  of  the  road,  the  proper  method  is  to  haul  the  most  of 
the  ballast  with  carts  or  on  the  contractor's  temporary  track  and 
spread  it  evenly  to  the  level  of  the  bottom  of  the  ties.  Then  the 
ties  and  rails  can  be  laid  and  a  construction  train  can  haul  what- 
ever ballast  is  required  for  surfacing  and  tamping.  When  the 
ties  and  rails  are  laid  on  the  bare  subsoil  and  the  construction 
trains  with  ballast  are  run  over  it,  the  rails  are  apt  to  become 
badly  bent  and  kinked.  A  compromise  between  the  above  methods 
is  to  use  light  construction  cars  which  may  run  on  the  standard 
gauge  track  without  doing  the  injury  that  would  be  caused  by 
standard  loaded  rolling  stock. 

Cost,  The  cost  of  ballast  depends  on  (a)  the  initial  cost  as  it 
comes  to  the  road,  (h)  on  the  distance  from  the  source  of  supply 
to  the  place  where   used,  and  {p)  on  the  method  of  handling.     A 


RAILROAD  ENGINEERING  115 

little  thought  will  show  the  variation  in  these  items  for  different 
roads,  and  therefore  any  estimates  of  cost  are  necessarily  approxi- 
mate. As  an  average  figure  the  cost  of  broken  stone  ballast  in 
the  track  may  be  computed  as  $1.25  per  cubic  yard,  and  the  cost 
of  gravel  may  be  put  at  60  cents.  The  cost  of  placing  and  tamp- 
ing gravel  ballast  is  estimated  at  20  to  24  cents,  while  the  similar 
estimate  for  cinders  is  put  at  only  12  to  15  cents.  The  cost  of 
loading  gravel  on  cars,  using  a  steam  shovel,  is  estimated  at  6  to 
10  cents  per  cubic  yard. 

105.  Ties.  The  cost  of  ties  to  a  railroad  is  too  apt  to  be 
superficially  considered  as  the  mere  market  price  of  the  ties  deliv- 
ered to  the  road.  The  true  cost  is  the  cost  of  the  maintenance  of 
suitable  ties  in  the  roadbed  for  an  indefinite  length  of  time.  The 
first  cost  is  but  one  item  in  the  total  cost.  A  cheap  tie  must  be 
soon  renewed.  The  labor  of  renewal  is  a  considerable  item  of  cost. 
The  renewal  disturbs  the  roadbed,  which  requires  adjustment  to 
keep  it  from  getting  uneven.  The  unavoidable  unevenness  of  the 
roadbed  has  an  actual  although  uncertain  effect  on  operating  ex- 
penses, increasing  the  fuel  consumption  and  wear  and  tear  on  the 
rolling  stock.     It  even  has  some  effect  on  possible  or  -safe  speed. 

In  round  numbers,  if  the  cost  of  buying  and  placing  a  good 
tie  is  twice  that  of  a  cheap  tie,  and  the  good  tie  lasts  twice  as  long 
as  the  cheap  tie,  the  economics  of  the  cases  are  nearly  equal.  But 
on  the  one  hand  we  have  the  interest  on  the  extra  cost  of  the  good 
tie  for  the  lifetime  of  the  cheaper  tie  and  on  the  other  hand  we 
have  the  additional  cost  of  maintenance  of  way  when  using  the 
poorer  ties  and  the  indefinite  increase  of  operating  expenses  due  to 
a  poor  roadbed.  The  annual  cost  of  a  system  of  ties  should  there- 
fore be  considered  as  the  sum  of  {a)  the  interest  on  the  first  cost, 
Q))  the  annual  sinking  fund  that  would  buy  a  new  tie  at  the  end  of 
its  life,  and  (c)  the  average  annual  maintenance  for  the  life  of  the 
tie,  which  includes  the  cost  of  laying  and  the  considerable  amount 
of  subsequent  tamping  that  must  be  done  until  the  tie  is  settled 
in  the  roadbed,  besides  the  regular  track  work  due  to  the  tie. 
Such  a  method  of  comparison  is  essential  in  considering  the 
economics  of  chemically  treated  ties  and  untreated  ties. 

Wood,  A  good  tie  must  last  as  long  as  possible  in  the  ground, 
must  be  hard  enough  not  to  be  unduly  affected  by  "rail-cutting," 


116  RAILROAD  ENGINEERING 

must  be  hard  and  tough  enough  to  hold  the  spikes,  and  finally 
must  be  reasonably  cheap.  Throughout  the  United  States  some 
of  the  varieties  of  oak  fulfill  these  conditions  (on  the  whole)  better 
than  any  other  kind.  Pine  is  the  second  choice,  largely  determined 
by  its  local  cheapness.  Cedar  and  chestnut  come  next,  while  red- 
wood, cypress,  hemlock,  tamarack  and  a  few  others  have  a  lesser 
use.  Redwood  and  cypress  are  as  good  as  any  from  the  standpoint 
of  mere  decay,  but  they  are  so  soft  that  the  rails  cut  them  and 
spikes  have  but  little  holding  power.  Since  spikes  must  be  driven 
within  a  very  small  area  on  the  face  of  the  tie  (for  the  tie  must  be 
placed  symmetrically  under  the  rails),  when  a  spike  is  partially 
pulled  up  by  the  rail  tending  to  turn  over,  the  spike  must  be  re- 
driven  very  near  its  former  position.  On  a  curve  there  is  a  very 
great  force  tending  to  turn  the  rail  over,  and  when  the  holding 
power  of  the  spikes  is  not  very  great,  they  must  be  frequently 
re-driven.  Forcing  them  down  in  the  same  hole  is  almost  useless. 
It  thus  happens  that  a  tie  of  soft  but  durable  wood  will  be  ''spike- 
killed  "  long  before  any  decay  has  set  in.  Redwood  ties  have 
been  largely  used  in  the  West,  and  when  they  are  protected  by  tie 
plates  from  rail-cutting,  their  life  in  a  dry  climate  is  very  great, 
especially  on  tangents. 

Dimensions,  Ties  for  standard  gauge  roads  are  8  feet,  8  feet 
6  inches,  and  occasionally  9  feet  in  length.     They  should  be  6 

inches  to  7  inches  thick,  and  if 
sawed  should  be  8  inches  or  9 
inches  wide.  If  they  are  hewed, 
they  should  have  a  hewed  face  of 
Fig.  85.  about  the  same  amount.     Sawed 

ties  are  a  practical  necessity  on 
trestles  and  bridges,  and  elsewhere  they  are  preferable.  When  ties 
are  cut  from  large  timber,  as  is  now  frequently  the  case,  sawing  is  a 
necessity,  but  there  is  a  general  opinion  that  hewed  "  pole  "  ties 
are  more  durable  than  sawed  ties.  In  any  case  the  bark  should 
be  entirely  removed  before  they  are  laid. 

Spacing.  The  most  common  spacing  is  24  inches  from  cen- 
ter to  center,  which  is  the  same  as  15  per  30 -foot  rail,  which  is  a 
common  way  of  stating  it.  As  many  as  20  per  30-foot  rail  are 
sometimes  used  if  the  ties  are  small,  but  as  this  means  only  18 


RAILROAD  ENGINEERING 


117 


inches  from  center  to  center,  the  space  left  for  tamping  is  small 
and  the  support  to  the  rail  may  be  even  less  than  that  given  by 
larger  ties  with  wider  spacing  and  more  perfect  tamping.  The 
spacing  should  not  be  exactly  even  as  more  support  is  needed  at  the 
joints.  Two  ties  are  placed  so  that  the  rail  joint  is  evenly  sup- 
ported by  them.  If  the  rail  joints  are  "  staggered,"  as  is  usual,  two 
more  joint  ties  are  placed  somewhat  closer  together  near  the  middle 
of  the  opposite  rail.  The  remaining  ties  of  the  allotment  (say  15) 
per  rail  will  be  divided  evenly  in  the  remaining  spaces. 

Rules  for  cutting.  It  should  be  required  that  hewed  ties 
should  have  their  two  faces  truly  parallel;  the  trees  should  be 
reasonably  straight,  one  rule  being  that  a  straight  line  passing 
through  the  center  of  one  end  and  the  center  of  the  middle  shall 
not  pass  outside  of  the  other  end ;  they  must  not  have  severe  splits 
or  shakes;  they  should  be  cut  in  winter,  or  when  the  sap  is  down; 
they  should  be  piled  for  at  least  six  months  before  being  used. 
When  ties  are  furnished  by  farmers  along  the  right  of 
way,  it  is  specified  that  the  ties  shall  be  neatly  piled 
crosswise  in  piles  on  ground  not  lower  than  the  rails, 
the  piles  to  be  at  least  seven  feet  from  the  rails. 

Rules  for  laying  and  reneuiing.  The  largest  and 
best  ties  should  be  reserved  for  joint  ties.  Whenever 
spikes  are  drawn  out,  the  hole  should  be  plugged  with 
a  wooden  plug  which  will  prevent  water  from  settling 
in  the  hole  and  thus  causing  rapid  decay.  Ties  should 
always  be  laid  at  right  angles  to  the  rail  and  never 
obliquely.  When  renewals  are  to  be  made,  the  requi- 
sitions are  to  be  based  on  an  actual  count  of  ties  to  be 
renewed  and  not  as  the  result  of  any  wholesale  estimate. 
It  is  unwise  to  use  a  mixed  variety  of  ties  in  the  track 
so  that  their  size,  elasticity  and  durability  are  very  dif- 
ferent.    This  will,  by  the  variation  in  elasticity,  cause  rough  riding. 

Cost,  Local  circumstances  very  greatly  affect  the  cost,  even 
for  the  same  class  of  ties.  Railroads  sometimes  succeed  in  monop- 
olizing the  tie  production  in  the  territory  through  which  they  run 
by  refusing  to  haul  ties  for  any  other  customer  or  railroad,  except 
at  prohibitory  rates,  and  control  the  price  somewhat  by  refusing 
to  pay  more  than  the  lowest  limit  at  which  the  local  people  will 


Fig.  86. 
Wooden 
Tie  Plug. 


118 


RAILROAD  ENGINEERING 


supply  the  ties.  The  best  ties  procurable  in  a  section  can  thus  be 
procured  for  45  to  50  cents  per  tie,  and  where  common  labor  is 
very  cheap  this  price  is  cut  even  to  25  cents.  On  the  other  hand, 
the  very  best  of  large  oak  ties  will  often  cost  75  to  SO  cents.  In 
view  of  the  above  variation  in  price,  any  estimates  must  depend 
on  local  conditions. 

io6.     Rails.     The  form  of  rail  section  popularly  known  as 
the  A.S.C.E.  section,  was  adopted  by  a  committee  of  the  American 

the  A.S.C.E.  section,  was  adopted 
by  a  committee  of  the  American 
Society  of  Civil  Engineers  in 
1893,  after  a  great  deal  of  discus- 
sion and  study.  That  form  is 
now  used  by  the  most  of  the  rail- 
roads of  the  country.  The  numer- 
ical dimensions  and  angles  shown 
in  Fig.  37  are  constant  for  all 
weights  of  rail.  The  letters  indi- 
cate the  variable  dimensions, 
which  are  given  in  the  following 
tabular  form : 


Pig.  87.    Am.  Soc.  C.  E.  Standard 
Rail  Section. 


Dimeir- 

sion, 

in  inches. 

Weight  per  yard  in  pounds. 

40 

45 

60 

65 

60 

65 

70 

75 

80 

85 

90 

95 

100 

A 
B 
CifeD 
E 
F 
G 

1% 

II 

% 

Iff 

2 

U 

m 

ItV 

2% 
3% 

H 

2tV 

2k 
if 

M 

2U 

IH 

2% 

n 

4M 

1/^ 

4tV 

M 

2% 

1/^ 

2tV 
If 

4% 
11 

2JI 

IH 

2M 
\\ 

411 
11 

2|f 

111 

2X 
If 
5 

% 
2% 
IX 

2^ 

If 
2% 

l|f 

2% 

tV 
5% 

If 
2ff 

m 

2H 

\\ 
2|f 

2% 

5% 
li 

m 

About  1909  the  American  Railway  Engineering  Association 
proposed  two  types  of  sections  (A  and  B).  Series  A  is  designed  to 
meet  the  wishes  of  those  who  desire  a  rail  with  a  comparatively  thin 
head  and  high  moment  of  inertia,  and  series  B  for  those  who  believe 
that  the  head  should  be  narrow  and  deep  and  that  the  moment  of 
inertia  is  comparatively  unimportant.  The  radius  of  the  upper 
corner  of  the  head  is  increased  from  \"  to  \" ,  The  side  of  the 
head,  instead  of  being  left  vertical,  has  a  flare  of  3°  35'  for  the  A 
type  and  3°  for  the  B  type.     In  1914,  the  Rail  Committee  reported 


RAILROAD  ENGINEERING 


119 


that  the  A.S.C.E.  sections  were  still  extensively  used  and  appar- 
ently had  not  been  largely  replaced  by  the  proposed  new  sections. 
The  feature  in  rail  design  which  has  excited  the  most  discussion 
is  the  radius  of  the  upper  corners  of  the  head.  Rail  wear  begins 
there  and  rails  with  sharp  corners  will  wear  longer  than  those  with 


..i*f 


Fig.  88,    Rail  Joint. 


larger  radii.  The  rapidity  of  the  rate  of  rail  wear  after  the  corner 
has  worn  off  is  one  proof  of  this,  and  so  from  the  maintenance  of 
way  standpoint  sharp  rail  corners  are  desirable.  But  excessively 
sharp  rail  corners  produce  excessive  wear  on  the  flanges  of  the  wheels, 
not  only  wearing  out  the  wheels  quickly  but  even  rendering  them 
dangerous  and  liable  to  cause  a  derailment.  The  compromise  of 
yq"  radius,  adopted  in  the  A.S.C.E.  design,  was  increased  to  \" 
in  the  A.R.E.A.  design. 

Weight,  The  weight  of 
rail  that  should  be  used  on  any 
road  is  an  exceedingly  important 
financial  and  technical  question. 
It  is  the  largest  single  item  of 
expenditure  in  the  construction 
of  a  road,  and  the  temptation  to 
cut*  down  the  item  by  5  per  cent 
or  10  per  cent  is  very  great.  For 
all  ordinary  sizes  the  price  per 
ton  is  uniform,  and  therefore  a  reduction  in  weight  per  yard  means 
a  corresponding  reduction  in  the  cost.  But  it  should  be  considered 
that  what  is  desired  is  a  rail  that  has  stiffness  and  strength^  no 
matter  how  much  it  weighs. 


Fig.  89.    Weber  Rail  Joint. 


120 


RAILROAD  ENGINEERING 


It  can  readily  be  proved  that  if  all  sizes  of  rails  had  exactly- 
similar  cross -sections  (which  is  nearly  true)  then  the  stiffness  of  a 
rail  varies  as  the  square  of  the  weight  and  the  strength  varies  as 
the  f  power.     This   means  that  if  we  add    10   per  cent  to  the 

weight  (and  therefore  to 
the  cost)  of  the  rail  we  are 
adding  21  per  cent  to  the 
stiffness,  and  over  15  per 
cent  to  the  strength.  As  a 
more  concrete  example, 
suppose  that  some  desire 
to  make  the  weight  of  the 
rail  for  a  road  60  lb.  per 
yard,  and  others  wish  to  use  a  70-lb.  rail.  At  $30  per  ton  (of 
2,240  pounds)  the  difference  of  cost  w411  be  $471.42  per  mile  of 
single  track.  But  on  the  other  hand,  although  the  cost  is  increased 
by  16§  per  cent,  the  strength  is  increased  26  per  cent,  and  the 
stiffness  is  increased  36  per  cent.  The  increase  in  stiffness  is  more 
than  double  the  increase  in  cost.  Unfortunately  there  is  no  ab- 
solute  criterion  as  to  the  amount  of  stiffness  or  strength  required 
since  it  depends  largely  on  the  unknown,  uncertain  and  variable 
tamping  of  the  ties  and  the  support  which  the  ties  receive  from 
the  ballast.  But  the  above  relative  figures  hold  good,  and  consid- 
ering  that  a  stiff  track  means  decreased  rolling  resistance,  higher 


Fig.  90.    Bonzano  Rail  Joint. 


Fig.  91.    Continuous  Rail  Joint. 


speed  and  greater  safety,  a  considerable  increase  in  weight  over 
that  minimum  on  which  it  would  be  possible  to  run  trains  is  not 
only  justifiable  but  is  a  measure  of  true  economy.  As  a  general 
statement,  it   may   be   said    that  60  lb.  per  yard  is  the  lightest 


132 


RAILROAD  ENGINEERING 


121 


weight  which  should  be  used  on  a  standard  gauge  road  running 
ordinary  rolling  stock,  no  matter  how  light  the  traffic.  Roads 
with  a  fair  business  should  have  70-lb.  rails.  The  great  trunk  lines 
are  relaying  with  100-lb.  rails  on  the  heavy  traffic  divisions,  and 
usually  have  as  heavy  as  85 -lb.  rails  on  all  but  the  small  branches. 

Length.  The  standard  specifications  proposed  by  a  committee 
of  the  American  Railway  Engineering  and  Maintenance  of  Way 
Association  in  1902  contained  this  clause:  "The  standard  length 
of  rails  shall  be  33  feet.  Ten  per  cent  of  the  entire  order  will  be 
accepted  in  shorter  lengths,  varying  by  even  feet  down  to  27  feet. 
A  variation  of  J-inch  in  length  from  that  specified  will  be  allowed." 


Fig.  92.    Wolhaupter  Rail  Joint  and  Section  Through  Center. 

During  late  years  much  experimenting  has  been  done  with  the 
idea  of  increasing  the  length  of  rail,  and  a  considerable  amount  of 
rails  of  45  and  even  60  feet  has  been  laid.  These  have  the  un- 
doubted advantage  of  saving  a  proportionate  number  of  rail  joints, 
which  are  always  a  source  of  trouble,  but  at  the  same  time  the 
allowance  for  expansion  which  must  be  made  at  every  joint  must 
be  proportionately  increased.  The  above  recent  standard  specifica- 
tion apparently  indicates  that  the  increase  in  length  has  not  proven 
desirable. 

107.  Rail  Joints.  The  action  of  a  heavy  wheel  rolling  on 
an  elastic  rail  is  to  cause  a  wave  of  elasticity  to  run  in  front  of  the 
point  of  contact.  A  perfect  track  is  one  that  will  keep  that  wave 
of  elasticity  perfectly  uniform,  which  requires  that  the  rail  joint 


122  RAILROAD  ENGINEERING 

should  have  the  same  strength  and  stiffness  as  the  rail.  Only  a 
welding  of  the  rails,  making  them  continuous,  would  accomplish 
this.  Any  rail  joint  which  is  as  strong  as  the  rail  is  necessarily 
much  heavier  and  stiffer.  Passing  by  the  older  forms  which  have 
now  become  obsolete,  we  have  in  Figs.  88  to  93  the  forms  which 
are  now  competing  for  adoption.  The  ''  angle  bar  "  is  still  used 
more  than  any  other  kind,  but  many  of  the  other  forms  have 
demonstrated  their  reliability  and  fulfilment  of  the  requirements 
as  nearly  as  may  be  hoped  for.  Nearly  all  of  these  designs  are 
used  exclusively  as  "suspended"  joints  rather  than  as  "sup- 
ported" joints,  the  difference  being,  as  the  name  implies,  that  a 
suspended  joint  is  placed  between  two  ties  so  that  each  end  of  the 
joint  has  an  equal  bearing  on  the  ties;  a  supported  joint  is  set 
directly  over  a  tie  and  hence  must  get  practically  its  whole  sup- 


Fig.  93.    Atlas  Suspended  Rail  Joint. 

port  from  that  one  tie,  unless  the  joint  is  so  long  that  it  rests  on 
the  adjacent  ties,  thus  making  it  a  "  three-tie"  joint. 

Angle  bars  are  usually  about  26  inches  long.  Of  course,  the 
bars,  of  whatever  kind,  should  be  so  made  that  they  will  fit  closely 
under  the  head  of  the  rail  and  also  have  a  close  fit  on  the  top  of 
the  flange.  This  means  that  every  rail  joint  must  be  made  with 
special  reference  to  the  particular  design  of  rail  with  which  it  is 
to  be  used  and  that  it  will  fit  no  other  design.  For  the  smaller 
sizes  of  rails  and  on  light  traffic  roads,  four-bolt  angle  bars  are 
used,  but  the  longer  and  heavier  bars  are  usually  made  with  six 
holes.  The  holes  are  made  in  a  somewhat  elliptical  form  and  the 
track  bolt  has  a  corresponding  form  immediately  under  the  head. 
The  bolt  is  thus  prevented  from  turning  when  the  nut  is  screwed 
on  or  off.     The  holes   in  the  rail  are  made  about  J  inch  larger  in 


134 


RAILROAD  ENGINEERING  123 

diameter   than   the  bolt.     This  is  to  allow  room  for  expansion  of 
the  rail  due  to  temperature. 

Insulated  Joints.  Rails  are  very  frequently  used  to  form 
an  electric  circuit  as  part  of  the  system  of  signaling.  As  an  item 
in  the  system  it  is  required  that  certain  joints  shall  be  so  made 
that  no  current  shall  pass 

between  adjacent  rails.  p<x&'V 
This  requires  the  use  of 
insulated  joints.     A  plate 
of    some    insulating   ma- 
terial  is  placed    between               

the  ends  of  the  rails  and  ^^*^¥^/| 

even    the    joint    bars,    of 
whatever   kind,  must   be 

_  -  .  .  p       p  Fig.  94.    Insulated  Joint  for  Track  Circuit. 

made  of  wood,  or  ir  oi 

metal  must  have  the  metal  insulated  from  the  rails.     One  form  of 

such  a  joint  is  illustrated  in  Fig.  94. 

io8.  Tie  Plates.  Many  of  the  soft-wood  ties  are  very  dura- 
ble as  regards  decay,  but  are  "cut"  by  the  rail  very  badly.  This 
is  not  due  to  mere  static  pressure  but  to  the  working  of  the  rail 
on  the  tie  during  expansion,  and  to  impact  when  the  rail  has 
become  loosened  somewhat  from  the  tie  and  a  wheel  load  suddenly 
forces  it  down  with  a  hammer  blow.  The  cutting  on  curves  is 
also  due  to  the  excessive  pressure  produced  by  the  edges  of  the 
flanges  which  is  developed  by  the  centrifugal  action  of  the  rolling 

stock.     Another  advantage  in  the 

use  of  tie  plates  lies  in  the  fact  that 

the  spikes  are  mutually  supported;  a 

spike  cannot   be    forced    laterally  in 

the  tie  without  drawing  the  tie  plate 

with  it  and  this  is  resisted  by  all  the 

Fig.  95.  Tie  Plate.  spikes  passing  through  the  tie  platCc 

The  cost  is  insignificant  compared 

with  the  added  life  of  the  tie,  especially  if  it  is  a  soft  wood  tie. 

The  advanta^^  with  an  oak  tie  is  not  so  great  proportionally. 

It  is  very  important  that  the  spikes  should  fit  the  spike  holes 
with  but  very  little  play,  otherwise  one  of  the  primary  objects  of 
the  plate  will  be  defeated,  and  the  rail  will  not  be  secure  against 


124 


RAILROAD  ENGINEERING 


Fig.  96.    Wolhaupter  Tie  Plate. 


lateral  motion.  Note  that  the  "flanges  on  the  lower  side  of  the 
plate  not  only  stiffen  it  and  inake  it  much  stronger  structurally 
but  they  also  secure  the  plate  to  the  tie  and  prevent  an  objection- 
able rattling.  The  very  presence  of  these  flanges,  however,  re- 
quires  that  the  plates  shall  be  pressed  or  hammered  on  to  the  tie 

until  the  flanges  penetrate  to 
their  full  depth.  This  may  be 
done  with  a  heavy  maul  but  it  is 
best  done  by  utilizing  the  hammer 
of  a  pile  driver. 

Notwithstanding    the    popu- 
larity of  flanged  tie  plates,  several 
up-to-date  roads  are  using  only 
tie  plates  with  flat  bottoms,  claim- 
ing that  the  punctures  made  by 
the  flanges  hasten  decay  or  crushing  under  the  plate,  which  is  avoided 
with  flat  plates.    A  flat  plate,  designed  for  use  with  screw  spikes 
(note  the  round  holes)  is  shown  in  Fig.  97. 

109.  Rail  Braces.  The  pressure 
against  the  outer  rail  on  a  curve,  and 
also  the  pressure  against  the  inner 
rail  when  a  train  stops  on  a  curve 
which  has  a  considerable  super- 
elevation, is  frequently  provided 
for  by  "rail  braces"  such  as  are 
illustrated  in  Figs.  99  and  100. 
Sometimes  these  are  made  of 
cast  iron,  but  these  are  brit- 
tle and  are  apt  to  be  broken 
by  a  blow  from  a  spike  maul 
when  the  spikes  are  driven. 
The  preferable  form,  although  it  is  more  expensive,  is  to  forge  them 
or  "press"  them  from  wrought  iron  or  steel.  In  Fig.  100  is  shown 
a  form  which  has  a  plate  which  runs  under  the  rail  which  thus 
makes  it  a  combined  rail  brace  and  tie  plate. 

110.  Spikes.  The  fundamental  requirement  of  a  spike  is 
holding  power,  but  it  must  also  be  cheap,  easily  applied,  and 
easily  removed  when  necessary.     It  has   been  found  that  mak- 


Fig.  97.     Economy  No.  9  RW 


RAILROAD  ENGINEERING 


125 


ing  the  surface  rough  and  even  jagged,  decreases  rather  than 
increases  the  holding  power,  and  also  destroys  the  fibre  of 
the  wood.  The  best  form  is  a  spike  with  plane  and  smooth 
faces.     The  point   should   be  made  so  as  to  cut  the  fibres  of   the 


Fig.  98.    Atlas  Tie  Plate. 


wood  instead  of  crushing  them.  By  this  means  the  fibres  are 
pressed  outward  and  downward,  and  thus  any  upward  pull  only 
tends  to  draw  the  fibres  back  to  their  original  place  and  so  increase 
the  pressure  against  the  spike  and  thus  increase  the  friction  and 
the  holding  power.    The  standard  spike  for  rails  weighing  more  than 


Fig.  99.    Atlas  Brace  KK. 


Fig.  100.    Atlas  Brace  K. 

56  pounds  per  yard  is  5 J  inches  long  and  -j^g-inch  square.  There 
will  be  about  375  in  a  keg  of  200  pounds.  On  this  basis,  if  the 
ties  are  24  inches  apart  and  four  are  used  per  tie,  there  will  be  re- 
quired 5,632  spikes  per  mile  or  28.16  kegs.     Of  course  a  consider. 


137 


126 


RAILROAD  ENGINEERING 


Fig.  101.    Track  Bolts. 


able  allowance  must  be  made  for  loss  and  waste  of  various  kinds. 

111.  Track  Bolts.  The  track  bolt  must  have  sufficient 
strength  to  hold  the  angle  plates  together  with  such  force  as  will 
develop  the  full  strength  of  the  angle  plates.     And  yet  this  must 

be  accomplished  so  that  the  friction  devel- 
"^>v  oped  will  not  be  so  great  that  the  rails  may 
L  ,y  J '  not  slide  in  the  joints  during  temperature 
r  I  changes.  On  a  straight  track  the  contrac- 
tive pull  due  to  a  fall  of  temperature  is  so 
great  that  no  possible  gripping  of  the  bolts 
could  prevent  slipping,  but  it  is  quite  possi- 
ble that  when  rails  expand,  and  especially 
when  on  a  curve,  the  resistance  to  slipping 
might  be  so  great  that  the  track  would 
bulge  out  of  alignment  instead  of  slipping 
at  the  joints.  Such  an  effect  does  actually 
take  place  when  the  allowance  for  expansion  is  insufficient  and  the 
rails  continue  to  expand  after  they  have  butted  end  to  end. 

Another  requirement  is  that  the  bolts  shall  not  turn  while 
the  nut  is  being  turned.  This  is  accomplished  by  an  enlargement 
of  the  bolt  just  under  the  head,  as  shown  in  Fig.  101.  This  fits 
fairly  closely  in  a  corresponding  oval-shaped  hole  in  the  angle 
plate.  The  sizes  shown  in  the  figure  are  about  what  should  be 
used  with  a  70  or  80-pound  rail.  Heavier  rails  require  a  longer 
bolt  and  one  that  is  proportionately  heavier.  The  type  of  rail 
joint  used,  and  also  the  type  of  nut  lock  if  any,  will  determine 
the  required  length  of  bolt,  while 
the  weight  of  rail  should  deter- 
mine the  diameter.  The  diam- 
eters vary  from  £  inch  to  1  inch, 
and  the  lengths  from  3  inches  to 
5  inches. 

112.  Nut  Locks.     There  are 

three  types  of  nut  lock — (^a)  those  which  have  an  elastic  cushion 
under  the  nut  which  absorbs  the  vibrations  that  would  otherwise 
loosen  the  nut,  (5)  those  by  which  the  nut  is  made  to  grip  the 
bolt  (by  some  unusual  device)  so  that  vibration  will  be  insufficient 
to  loosen  it,  and  (c)  the  "positive"  type,  in  which  the  locks  arepre- 


Fig.  102.    Ajax  Tail  Washer. 


138 


RAILROAD  ENGINEERING 


127 


vented  from  turning  by  some  definite  and  positive  mecLianical  check. 

The  ''  Ajax  Tail  Washer,"  shown  in  Fig.  102,  is  a  sample  of 
the   first  class,  although  it   also   has  some  of  the  elements  of  the 
third  class,  since  the  sharp  steel  points  will  tend  to  bite  into  both 
the  under  side  of  the  nut 
and^the  side  of  the  angle 
plate   where    it    rests 
whenever  there  is  a  tend- 
ency for  the  nut  to  turn 
backward.    These  points 
merely  drag  and   slip 
when   the  nut  is  being 
tightened. 

The  Columbia  nut  lock,  shown  in  Fig.  103,  is  a  sample  of 
the  second  class.  The  nut  is  compound,  the  inner  piece  being  a 
four-sided  frustum  of  a  pyramid,  the  edges  being  rounded.  This 
fits  into  a  corresponding  recess  in  the  outer  piece.  The  inner 
piece  is  also  cut  through  so  that  it  may  be  slightly  squeezed 
together.  The  pyramidal  form  requires  both  pieces  to  turn  to- 
gether. When  the  outer  piece  comes  in  contact  with  the  angle 
plate  it  is  forced  back  (relatively  to  the  inner  piece)  which  squeezes 


Fig.  103.    Columbia  Nut  Lock. 


Fig.  104.    Gordon  Nut  Lock. 

the  inner  piece  together  and  causes  it  to  grip  the  bolt.     The  more 
the  nut  is  turned,  the  tighter  the  grip. 

The  Gordon  nut  lock,  shown  in  Fig.  104,  is  a  sample  of  the 
third  class,  although  it  is  designed  to  be  used  only  w^ith  the  form 
of  angle  plate  which   is  shown.     In  the  form  shown  the  square 


128 


RAILROAD  ENGINEERING 


nuts  must  be  turned  until  one  edge  is  exactly  on  line.  A  one- 
eighth  turn  forward  or  back  will  always  accomplish  this.  Thus 
when  the  bar  is  slipped  in  all  nuts  are  absolutely  prevented  from 
turning.  The  above  designs  have  been  selected  as  mere  samples 
of  each  class  from  a  great  multitude  of  designs  of  greater  or  less 
merit  which  are  on  the  market. 


LAYING  TRACK. 

113.  Surveying.  After  the  earthwork  is  completed  and  the 
culverts  and  bridges  are  built,  the  center  line  of  the  track  must  be 
re-located  on  the  roadbed  surface  of  the  fills  and  cuts.  Reference 
points  should  have  been  established  during  the  original  survey  so 
that  by  the  intersection  of  two  radii  swung  from  permanently 
established  points  the  beginnings  and  endings  of  all  curves  may 
be  re-located.  Then  all  intermediate  stations  should  be  filled  in. 
A  line  of  levels  should  then  be  run   and  the  an-reement  of  these 


•  RIGHT.  WRONG. 

Fig.  105.    Right  and  Wroug  Method  of  Laying  Ties. 

levels  with  the  designed  grade  should  be  determined.  If  the  levels 
of  the  cuts  and  fills  has  been  followed  with  sufficient  closeness 
during  construction,  there  should  be  no  discrepancy  except  that  the 
levels  of  fills  should  be  somewhat  higher  than  that  called  for  so  as 
to  allow  for  subsequent  settlement. 

114.  Laying  Ballast.  This  has  already  been  discussed  in 
§104,  as  has  also  the  policy  of  laying  the  ties  and  rails  first  and 
then  drawing  the  ballast  in  a  construction  train  on  the  poorly 
supported  track. 

115.  Laying  Ties.  If  the  ties  have  been  sawed  to  an  exact 
length,  the  alignment  of  one  end  will  of  course  line  up  the  other 
but  when  ties  have  been  hewed  and  chopped  off  and  sometimes  even 
when  they  have  been  sawed,  there  is  a  range  of  several  inches  in 
their  length  and  then  it  is  required  that  they  shall  be  aligned  at 
one  end  or  the  other.     A  little  stick  may  be  furnished  the  track- 


RAILROAD  ENGINEERING  129 

men  as  a  spacer,  but  with  a  little  experience  they  will  space  the 
ties  as  closely  to  the  required  spacing  as  is  necessary.  The  ties 
should  always  be  laid  with  rings  convex  upward  rather  than  con- 
cave. Of  course  a  pole  tie,  when  it  is  perfectly  symmetrical,  will 
be  the  same  either  way,  but  there  is  usually  a  choice,  as  is  shown 
by  the  figure.  When  the  rings  are  concave  upward  there  is  a 
greater  chance  for  water  to  soak  in  and  cause  decay.  Turning  the 
tie  the  other  way,  the  w^ater  will  shed  off  more  freely. 

ii6.  Laying  Rails.  Rails  should  be  laid  so  that  the  joints 
are  staggered  as  nearly  as  possible.  This  requires  a  half-rail  length 
at  the  start.  But  the  difference  of  length  of  the  outer  and  inner 
rails  of  a  curve  will  disturb  the  arrangement  of  the  joints,  no 
matter  how  perfectly  it  may  start.  These  differences  may  be  neu- 
tralized by  selecting  rails  which  are  a  foot  or  tw^o  shorter  than  the 
usual  length.  But  the  occurrence  of  a  switch  will  require  a  read- 
justment of  the  joints,  and  may  require  a  rail  cutting  so  as  to  bring 
a  joint  where  desired.  Yery  short  lengths  of  rail  should  be 
avoided.  If  a  full  length  rail  comes  a  few  feet  short  of  a  point 
where  a  joint  'tnust  be  made,  it  should  be  cut  so  that  both  pieces 
shall  have  a  fair  length.  The  rails  are  first  laid  approximately  in 
position  and  end  to  end. 

When  placing  the  joints  on  the  rails,  allowance  must  be  made 
for  rail  expansion  due  to  temperature.  The  theoretical  amount  to 
be  allowed  is  .0000065  of  the  length  for  each  degree  Fahrenheit. 
If  it  could  be  readily  determined  just  what  is  the  temperature  of 
the  rail  (w^hich  is  possibly  much  higher  than  that  of  the  air)  at  the 
time  the  rail  is  laid  and.  also  the  highest  and  lowest  temperature 
that  it  will  ever  attain,  the  problem  would  be  comparatively  simple, 
but  the  fact  that  these  quantities  are  so  uncertain  seem  to  render 
useless  any  attempt  at  an  exact  calculation  and  to  justify  the  rough 
and  ready  rule  of  '-allowing  -f^  inch  for  coldest  w^eather,  J-inch 
during  the  spring  and  fall,  and  J^ -inch  during  the  very  hottest 
w^eather."  The  allow^ance  of  yig-inch  during  the  very  hottest 
weather  is  apparently  based  on  the  idea  that  the  rails  should  never 
be  allowed  to  butt  up  against  each  other,  for  then  any  additional 
expansion  will  cause  the  rails  to  buckle.  If  a  rail  was  laid  when 
its  actual  temperature  was  60°  F.,  its  length  of  33  feet  would  be 
increased  by  about  ^  inch    if    its    temperature    were    raised    to 


130  RAILROAD  ENGINEERING 

120°,  as  might  readily  happen  under  a  burning  summer  sun  when 
the  temperature  of  the  air  in  the  shade  was  perhaps  100°.  A  prac- 
tical method  of  making  an  allowance  which  would  be  sufficiently 
accurate  would  be  as  follows:  Place  a  bulb  thermometer  (one 
without  a  metal  frame)  so  that  the  bulb  lies  against  the  rail  ana 
then  cover  it  up  so  as  to  protect  it  from  the  air  and  so  that  it  will 
assume  the  temperature  of  the  rail  as  closely  as  possible.  The 
expansion  of  a  33-foot  rail  for  each  degree  is 

.0000065  X  33  X  12  =-  .002574  inch. 

If  w^e  allow  120°  (some  allow  150°)  as  the  maximum  beyond 
which  it  is  assumed  that  the  temperature  will  never  rise,  then  the 
difference  between  this  maximum  and  the  ascertained  temperature 
of  the  rail,  when  multiplied  by  the  above  allowance  per  degree, 
equals  the  gap  to  be  allowed  at  each  joint.  Strips  of  sheet  metal 
of  the  required  thickness  should  be  furnished  to  the  trackmen. 
These  strips  are  placed  temporarily  between  the  rail  ends  which 
obviates  any  necessity  for  measuring  on  their  part.  When  the 
joints  have  been  bolted  up,  one  line  of  rails  is  spiked  so  that  they 
are  at  the  proper  distance  from  the  ends  of  the  ties.  Then  by  using 
a  "track  gauge"  at  every  other  tie  the  other  line  of  rails  may  be 
spiked  down.  The  intermediate  ties  are  then  spiked.  "  Standard" 
gauge,  which  is  in  almost  universal  use  in  this  country,  is  4  feet 
8^  inches  =  4.708  feet.  Although  the  gauging  should  be  all  right 
for  these  other  ties,  the  gauge  should  be  at  hand  to  check  the 
previous  work,  especially  if  it  is  on  a  sharp  curve.  Track  instruc- 
tions  frequently  specify  that  rails  should  be  previously  bent  before 
laying  around  curves,  or  in  other  words,  that  the  rails  should  have 
the  proper  curve  when  lying  freely  on  the  ties.  Of  course  the 
necessity  for  this  increases  with  the  degree  of  curvature,  it  being 
unnecessary  for  very  easy  curves. 

The  practical  trouble  comes  at  the  joints;  the  rails  instead  of 
having  a  common  tangent  will  intersect  at  an  angle  which  is  de- 
structive both  to  the  track  and  the  rolling  stock  when  trains  are  run 
at  high  speed.  The  ideal  method  is  to  have  the  rail  bending  done 
by  rollers  in  a  rolling  mill  and  this  method  is  almost  a  necessity 
for  the  very  sharp  curvature  employed  on  some  electric  roads. 
The  field  method  is  to  use  a  "rail  bender"  which  bends  the  rail  in 


RAILROAD  ENGINEERING  131 

lengths  of  about  two  feet  and  which  must  be  operated  very  care- 
fully and  skilfully  to  avoid  ruining  the  rail.  A  rail  is  bent  until, 
when  a  string  is  stretched  from  the  inside  of  the  head  at  one  end 
to  the  inside  of  the  head  at  the  other  end,  the  distance  from  the 
middle  point  of  the  string  to  the  inside  of  the  head 
at  the  middle  of  the  rail  is  as  computed  below: 

In   Fig.    106,   since  the  triangles    AOE    and 
ADC  are  similar,  AO  :  AE  ::  AD  :  DC,  or  E  = 

-^  AD^  -f-  X.     When  as  is  usual,  the  arc  is  very 

short  compared   with   the  radius,   AD  =  -^  AB  ^^'  ^^^' 

very  nearly.     Making  this  substitution,  we  have 

Inverting  the  formula  we  have  the  formula  required  for  present  use: 

chord^  ,  ,   .  ,      . 

X  =  -g^  (very  nearly)  (55) 

Although  not  mathematically  accurate,  the  maximum  error  in  any 
practical  case  is  far  within  the  attainable  accuracy  using  a  string. 

Example.  What  should  be  the  middle  ordinate  for  the  outer 
rail  (83  feet  long)  for  a  6  degree  curve  ?  We  will  call  the  chord 
33  feet  since  the  slight  inaccuracy  involved  only  tends  to  neutral- 
ize the  inaccuracy  of  the  fornriula.  R  =  955.37  +  2.35  =  957.72. 
Then  33^  (which  equals  1089)  divided  by  (8  X  957.72)  =  .142 
foot  or  1.70  inches.  If  a  similar  calculation  is  made  for  the  inside 
rail  the  difference  in  the  ordinate  is  less  than  .01  inch,  which  shows 
that  unless  the  curvature  is  excessively  sharp  there  is  no  need  to 
make  the  allowance  for  half -gauge  (2.35,  as  is  done  above)  nor  even 
to  use  great  accuracy  in  the  decimals.  A  table  giving  the  middle 
ordinates  for  33-foot  rails  for  different  degrees  of  curvature  is  a 
desirable  part  of  the  equipment  of  each  track  foreman. 

The  spikes  on  the  opposite  sides  of  a  rail  should  be  driven 
"  staggering,"  so  that  there  will  be  less  tendency  to  split  the  tie. 
The  direction  of  the  staggering  should  be  reversed  at  the  two  ends 
of  the  tie,  so  as  to  prevent  a  loosening  of  the  hold  of  the  spikes, 


132 


RAILROAD  ENGINEERING 


such  as  would  occur  if  the  reverse  method  were  used  and  the  tie 
were  to  become  displaced  and  not  perpendicular  to  the  rails.  Such 
an  item  of  construction,  while  very  simple,  is  of  vital  importance. 

117.  Surfacing.  Track  centers  (stakes)  having  been  placed 
in  line,  the  alignment  of  the  track  is  made  perfect.  The  rail  lay- 
ing should  have  been  done  with  the  rails  a  few  inches  below  their 
proper  gi-ade.  Then  jacks  are  placed  under  the  ties  (or  rails,  as 
most  convenient)  and  the  track  is  raised  to  grade,  as  given  by 
grade  stakes  which  should  have  been  previously  set.  Using  tamp- 
ing picks  or  shovels,  the  ballast  is  jammed  under  the  ties  until 
,      .  they  are  solid  at  the  desired  grade.     Picks  or 

^m^  tamping  bars  are  best  for  tamping  broken 

J^        ^^  stone  ballast,  but  gravel  can  be  most  easily 
|HL   ^W     tamped  with  shovels. 

fl^Bj^F^  118.     Super-elevation  of  the  Outer  Rail 

^^^|V  on  Curves.     It  is  one  of  the  demonstrations 

^^HT  of  physics  that  the  force  required  to  make  a 

^^g^  mass  move  in  a  circular  path  equals  QiV^  -^ 

|H^  ^R,  in  which  G  is  the  weight,  v  the  velocity 

^H  in  feet  per  second,  g  the  acceleration  of  the 

^Ml  force  of  gravity  in  feet  per  second  in  a  sec- 

^^^SSk.  Olid,  and  R  the  radius  of  curvature.     If  the 

^^^^^^P  rails  on  a  curve  were  level  transversely,  such 

a  force  could  only  be  furnished  by  the  pres- 
sure of  the  wheel  flanges  against  the  rail.     To 
avoid  this  objectionable  pressure,  the  outer 
rail  is  elevated  until  the  inward  component  of  the  inclined  wheel 
pressure  equals  the  computed  centripetal  force  required. 

In  Fig.  108,  oh  may  represent  the  resultant  pressure  on  the 
rails  at  the  same  scale  at  which  oc  represents  the  weight  G.  Then 
ao  is  the  required  centripetal  force.  From  similar  triangles,  we 
may  write  nn  :  sm  w  ao  :  oc.  Call  g  =  32.17.  Call  R  =  5730 
-r-  D,  which  is  sufficiently  accurate  for  the  purpose.  Call  v  == 
5280 Y  -^  3600,  in  which  V  is  the  velocity  in  miles  per  hour. 
77in  is  the  distance  between  rail  centers,  which  for  an  80-lb.  rail 
and  standard  gauge  is  4.916  feet;  sm  is  slightly  less  than  this.  As 
an  average  value,  call  it  4.900,  which  is  its  exact  value  when  the 
superelevation  is  4|  inches.     Calling  sn  =  e,  we  have 


Pig.  107.    Trip  Ballast 
Gang  Jack 


RAILROAD  ENGINEERING 


133 


ao        .  ^^  Gv    1 
e  =  S7/1  —  —  4.9  — T^  -77- 
OG  gli    G 


e  =  .0000572V^D 


4.9  X  528Q^V^D 
32.17  X  3600^  X  5780 
(56) 


>«-%c 


Studying  the  above  formula,  it  will  first  be  noticed  that  the 
required  super-elevation  varies  as  the  square  of  the  velocity,  which 
means  that  a  change  of  velocity  of  only  10  per  cent  would  require 
a  change  of  super-elevation  of  21  per  cent.  Since  train  velocities 
over  any  road  are  so  very  variable,  it  shows  that  it  is  impossible  to 
make  any  super-elevation  fit  all  trains  even  approximately.  There 
are  several  approximations  in  the  above  formula,  but  none  of  th3m 
will  affect  the  result  as  much  as  a  change  of  less  than  one  per  cent 
in  the  velocity. 

Practical  Rules.  A  very  simple  and  commonly  used  rule  is 
to  elevate  one  inch  for  each  degree  of  curvature.  This  rule  agrees 
with  the  above  formula  when  the  velocity 
is  about  38  miles  per  hour.  If  a  train  is 
running  slower  than  the  speed  for  which 
the  super-elevation  was  designed,  the 
practical  efiect  is  to  relieve  the  pressure 
against  the  outer  rail  which  still  Q;xists  in 
spite  of  super-elevation  on  account  of  the 
necessity  of  turning  the  groups  of  four 
or  six  wheels  under  a  truck  or  engine. 
Therefore  the  better  plan  is  to  elevate  for 

the  fastest  trains.  Thirty-eight  miles  an  hour  is  so  near  the  max- 
imum for  a  light  traffic  branch  line,  that  the  above  rule  is  very  fair, 
although,  of  course,  not  so  good  as  a  more  accurate  one. 

Another  rule,  which  is  especially  good  for  track  maintenance 
when  the  track  foreman  may  not  even  know  the  degree  of  curve,  is 
developed  as  follows:  Assume  that  a?  in  equation  55  is  equal  to  e 
in  equation  56,  and  we  have 


Fig.  108. 


chor(P 
~8R" 


.0000572  Y^D 


but  since   D  =  5730  -^  R,  we  have 
chord'  =  2.621  Y'  and 
chord  =  1.62  V 


(57) 


134 


RAILROAD  ENGINEERING 


Assume  that  the  limit  of  50  miles  per  hour  is  set  as  the 
speed  of  the  fastest  trains,  then  chord  =  1.62  X  50  =  81  feet. 
This  means  that  if  a  string  or  tape,  having  a  length  of  81  feet,  is 
stretched  between  two  points  at  that  distance  apart  on  the  inner 
head  of  the  outer  rail,  the  length  of  the  ordinate  at  the  middle  of 
the  string  equals  the  required  super-elevation  for  50  miles  per 
hour.  Similar  computations  can  be  made  and  tabulated  for  all 
other  desired  speeds.  On  double  track,  since  the  speed  on  an 
ascending  grade  will  almost  certainly  be  less  than  the  speed  of 
trains  coming  down  that  grade,  there  should  theoretically  be  a 
difference  in  the  super-elevation  to  allow  for  this  difference  of 
speed.  On  some  roads  the  track  instructions  contain  specific 
instructions   to  allow   for  this. 

SWITCHES   AND   TURNOUTS. 

up.  Switch  Construction.  The  universal  method  of  keep- 
ing the  wheels  of  railroad  rolling  stock  on  the  rails  is  to  put 


Pig.  109.    Stub  Switch. 


Fig.  110.    Point  Switch. 


flanges  on  the  inner  edges  of  the  w^heels.  When  the  wheels  are  to 
be  led  away  from  the  main  track,  it  must  be  done  by  creating  a 
new  pathway  for  these  flanges.  This  is  done  by  leading  the  wheel 
flanges  through  the   rails  or  by  raising  the  wheels  sufficiently  so 


RAILROAD  ENGINEERING  135 

that  they  may  pass  over  the  rails.  Both  methods  will  be  de- 
scribed. The  method  of  leading  the  flanges  through  the  rails  is 
most  commonly  used  since  it  does  not  require  raising  the  rolling 
stock  over  the  rail.  \ 

AYhen  the  rails  are  first  led  out  from  the  main  track,  it  must  be 
done  by  one  of  two  general  methods,  the  stub-switch  method, 
illustrated  in  Fig.  109,  or  by  the  point-switch  method,  illustrated 
in  Fig.  110.  Of  course  these  figures  are  only  diagrammatic  and 
it  should  be  at  once  understood  that  in  these  figures  as  well  as  in 
many  others  in  this  chapter,  it  has  been  necessary  to  use  very 
short  radii,  very  wide  gauge,  and  very  large  frog  angles  in  order 


Fig.  111.    Details  of  Point  Switcli. 

to  illustrate  the  principles   by  figures  which  are  suitable  for  the 
page  and  which  would  at  the  same  time  be  intelligible. 

The  use  of  the  stub  switches  is  now  confined  to  the  cheapest 
of  yard  work  or  private  switches  which  run  off  from  sidings.  They 
should  never  be  used  in  any  main  track.  Their  construction  may 
be  implied  from  Fig.  109.  The  pair  of  movable  rails  are  tied 
together  at  the  proper  gauge  by  tie  rods.  The  two  pairs  of  stub 
ends  are  of  course  fixed.  The  details  of  a  point  switch  are  illus- 
trated in  Fig.  111.  Note  that  one  rail  on  each  side  is  absolutely 
unbroken.  The  other  rail  has  nearly  all  of  the  head  cut  away  and 
a  part  of  one  flange.  The  other  flange  and  the  web,  with  that 
part  of  the  head  immediately  over  the  web  still  remains.  The  tie 
rods  which  are  clearly  shown  connect  this  pared-down  rail  with  a 


136 


RAILROAD  ENGINEERING 


similar  rail  on  the  other  side.  The  last  tie  rod  has  an  extension 
to  which  the  switch  rod  from  the  switch  stand  is  attached.  The 
moving  rail  slides  on  tie  plates  which  have  rail  braces  on  the  outer 
ends  which  stiffen  the  rail  against  the  unusual  lateral  strain  to 
which  it  is  subjected.  The  angle  of  these  switch  points  varies  from 
0°  52'  to  2°  36'. 

/Switch  Stands,     One   type  of  switch  stand,  which  also  com- 
bines a  semaphore  (or  signal  which  shows  its  position)  is  shown  in 


Fig.  113.    Switch  Stand. 

Fig.  112.  The  mechanism  is  of  course  covered,  the  cover  being 
indicated  by  the  faint  lines.  The  type  shown  is  but  one  of  a 
multitude  for  which  there  is  no  space  here. 

Guard  Bails.  These  are  shown  opposite  the  frogs  in  both 
Figs.  109  and  110.  They  obviate  any  danger  of  the  wheel  run- 
ning on  the  wrong  side  of  the  frog  point  and  also  save  the  frog 
point  from  excessive  wear.  The  flange-way  space  between  the 
heads  of  the  guard  rail  and  the  wheel  rail  must  therefore  not 
exceed  a  definite  quantity,  which  is  made  about  two  inches.  Since 
this  is  less  than  the  distance  between  the  heads  of  two  ordinary 
sized  rails  when  placed  base  to  base,  to  say  nothing  of  any  space 


RAILROAD  ENGINEERING 


137 


for  spikes,  the  base  of  the  guard  rail  must  be  cut  away  somewhat. 
These  guard  rails  are  made  from  10  to  15  feet  long  and  are  bent  a 
few  feet  from  each  end  so  that  there  shall  be  no  danger  that  a 
wheel  flange  shall  strike  the  ends. 

Frogs.  When  the  outer  switch  rail  reaches  the  opposite 
main  rail,  the  wheel  flange  must  either  pass  through  the  head  of 
the  main  rail  or  the  wheel  must  be  raised  so  that  the  flange  may 
pass  over  the  rail.  The  most  commonly  used  frogs  are  those  of  the 
type  of  which  the  wheel  flange  passes  through  the  head  of  the  rail. 
The  geometrical  outline  of  such  a  frog  is  shown  in  Fig.  113. 

The  frog  number  may  be  found  by  dividing  the  distance  from 
the  *'  point "  to  any  chosen  place  by  the  width  of  the  frog  at  that 
place,  or  in  the  figure  ch  -f-  ah.  But  since  c  is  the  imaginary 
intersection  of  the  sides  produced  and  is  not  easily  determinable 
with  accuracy  on   the   frog,  it  is  sometimes  easier  to  measure  the 


Fig.  113.    Diagram  of  Frog. 

width  at  two  places  {ed  and  ah)  and  then  divide  the  sum  of  those 
widths  by  the  total  distance  sh\  this  will  give  the  same  result  as 
before.  This  measuring  may  be  done  with  any  convenient  unit  of 
length  such  as  a  pencil  or  a  spike.  Find  the  place  where  the 
width  of  the  frog  just  equals  the  unit  of  length  and  then  step  off 
that  distance  to  the  "  point."  The  fundamental  objection  to  all 
frogs  of  this  type  is  that  they  make  a  break  in  the  main  rail 
which  causes  a  jar  when  a  train  is  run  over  the  frog  at  high  speed. 
If  the  frog  is  made  "  stiff"  as  is  illustrated  in  Fig.  114,  the  track 
has  the  advantage  of  being  literally  stiff,  but  the  wheels  have  to 
run  over  the  gap.  The  design  shown  in  the  figure  aims  to  obviate 
any  drop  of  the  wheel  at  any  point  and  this  will  be  fairly  accom- 
plished as  long  as  the  hardened  steel  faces  can  resist  the  wear 
which  is  very  severe  in  the  older  and  commoner  designs. 


138 


RAILROAD  ENGINEERING 


The  '' spring-rail"  frog,  illustrated  in  Fig.  115,  is  an  attempt 
to  obviate  the  gap  for  main  line  trains.  Wheel 
flanges  running  on  to  the  switch  force  back  a  por- 
tion  of  the  main  track  rail  which  is  normally  held 
in  place  by  a  heavy  spring.  Running  on  to  the 
switch  is  supposed  to  be  done  at  comparatively 
slow  speed,  which  permits  the  rail  to  be  forced 
back  without  danger  of  derailment.  But  since 
the  main  rail  is  kept  in  place  by  the  pressure  of  a 
spring,  the  frog  lacks  the  stiffness  of  a  "stiff"  frog. 
The  method  of  raising  the  wheel  and  carrying  it 
over  the  main  rail  is  illustrated  in  Fig.  116,  which 
shows  one  of  the  many  devices  to  accomplish  this 
end.  The  method  has  the  very  positive  advantage 
of  leaving  the  main  track  absolutely  unbroken. 

In  Fig.  117  is  shown  a  method  of  avoiding  a 
break  even  at  the  switch.  The  switch  rails  are  at 
the  level  of  the  main  rails  at  the  switch  point  but 
gradually  rise  higher  until  the  wheel  flange  is 
high  enough  to  cross  over  the  main  rail.  Such 
a  switch  must  be  operated  at  slow  speed. 

120.  Mathematical  Design.  In  all  of  the 
following  demonstrations,  the  track  lines  repre- 
sent the  gauge  lines  or  the  lines  of  the  inside 
head  of  the  rails.  The  older  formulae,  which  are 
still  in  extensive  use  on  account  of  their  simplic- 
ity, all  assume  that  the  switch  rails  are  bent  to 
arcs  of  simple  curves  extending  from  the  switch 
point  to  the  frog,  and  that   they  are   tangent  to 


Section  A-A 
Fig.  114.    Anvil-face  Frog. 

the  main  rails  at  the  switch  point.     On  account  of  its  common 
use  and  also  because  it  forms  a  fitting  introduction  to  the  more 


RAILROAD  ENGINEERING 


139 


exact  method,  it  will  be 
given.  In  all  of  the  fol- 
lowing demonstrations, 
the  following  notation 
will,  for  simplicity,  be 
kept  uniform.  R  will 
represent  the  radius  of 
curvature  of  the  main 
track,  if  it  is  curved, 
and  r  is  the  radius  of 
the  switch  rails.  F  will 
always  represent  the  frog 
angle,  and  a  the  gauge 
of  the  track.  L  will  rep- 
resent the  "lead"  or  the 
distance  measured  on 
the  main  track  from  the 
switch  point  B  to  the 
frog  point  F. 

The  angle  FDD  in 
Fig.  118  equals  the  angle 
F,  and  BD  is  the  versed 
sine  of  F  to  the  radius 
FO.  From  this  relation 
we  may  derive  the  equa- 
tion 

2  ^      vers  1  ^      ^ 
also,  since  BF  -^  BD  = 

cot-^F,  BD  =  g  and 

BF  =  L,  we  have 

L  =  ^cot-^F       (59) 
Also, 

L=  [r  -{-  -jg)  BinF 

(60) 


o 


140 


RAILROAD  ENGINEERING 


and 


QT=  2r8m~^F 


(6l) 


All  of  the  above  formulae  involve  the  angle  F.  Reference  to  Table 
III*  will  shov^'  that  with  one  chance  exception  the  values  of  F  are 
always  odd  and  the  accurate  computation  of  their  trigonometrical 
functions  is  tedious.  Fig.  119  shows  that  the  ratio  of  the  length 
to  width  of  a  frog,  or  jr?^  -r-  ah,  which  is  called  ??,  is  also  equal  to 

-p-  cot  -jy-  F.     This  relation   can  be  used  to  derive   the  following 

marvellously  simple  formulae: 


i 

1 

1 

^^H^^^^^^HS^^^^^^^^^^hVS 

1 

Fig.  116. 

1     ,  14 

Since  L  =  y  cot-^  P^,  and  n  =  -— cot-^  F,  we  may  at  once 


derive  the  equation 


L  =  2gn 


(62) 


But  in  Fig.  120  the  line  QZ,  drawn  midway  between  the  rails, 
bisects  DF  at  Z  and  also,  since  DQ  is  one-half  of  DB,  QZ  is  one- 
half   of   BF  or  =  -g-L.     OQ  =  r  and  the  angle  ZOQ  = -^  F. 

♦See  Webb's  "Trigonometric  Tables,"  pubUshed  by  American  School  of  Correspond- 
ence, Chicago,  111.    Price,  50c. 


RAILROAD  ENGINEERING 


141 


Then  r  -^  -^Ti  =  cot  -j-  F,  from  which 

/'  =  nJj 
Combining  equations  61  and  62,  we  have 

7'  =  2gn^ 


(63) 


(64) 


The  above  relations  only  lack  the  merit  of  correctness  of 
application  to  make  the  whole  subject  very  simple.  They  were 
first  devised  when  stub  switches  were  in  universal  use  and  although 


Fig.  117. 

it  is  theoretically  possible  to  make  a  stub  switch  conform  to  these 
lines,  it  is  impracticable  even  there.  But  with  point  switches, 
which  are  in  almost  universal  use,  the  switch  rail  makes  an  angle 
varying  from  0°  52'  to  2°  36'  with  the  main  rail.  The  frog  rails  are 
also  made  straight. 

The  effect  of  each  of  these  changes,  taken  separately,  is  to 
shorten  the  lead.  The  combined  effect  is  to  shorten  the  lead  from 
15  to  25  per  cent.  In  Fig.  121,  DM  represents  the  straight  point 
rail  and  HF  the  straight  frog  rail,  the  two  being  connected  by  the 


142 


RAILROAD  ENGINEERING 


arc  MH,  tangent  to  both.     The  central  angle  of  this  arc  is  there- 
fore (F  -  a),  a  being  the  angle   (MDN)   of  the  point  rail.     The 

chord  MIX  makes  an  angle  with  the  main 

rails  which  equals 

Call  FH  =/and  MN  :=  A-.  Then  HM  sin 
-^(F  +  a)  =  ^-/sin  F-^.     But  HM  = 

(^  +  -g-  ^)  ^  sin  -g-  (F  -  a).     Substituting 
this  value  of  HM  in  the  previous  equation 
and  solving  for  (^  +  -9-^)  we  have 
^-/sinF->^ 


Fig.  118. 


(^  -f  4  '^^)  = 


2  sin  -^  (F  +  a)  sin  -^  (F  -  a) 


(65) 


_g  -,/'sin  ¥  -k 
cos  a  —  cos  F 

ST=2rsin-i(F-a)   (66)    ^ 
The  lead  BF  =  L  =  HM  cos  -i 


(F  +  a)+/cosF  +  DN 


Fig.  119 


o"--     - 


.^> 

• 
1 

F   I 

X  '  \ 

.\  1 

A      \ 

_\\ 

_,  »'T 

-\f\ 

^''            \ 

^  \  ' 

i  \ 

-B 

1 

Fig.  120. 


=:(^-/sin  F-^)cot-^(F  +  a)  +/ 

cos  F  +  DN  (67) 

If  (^  +  -9-  ^)  has  already  been  computed 

numerically  from  equation  65,  it  will  be 
more  simple  to  compute  L  as  follows: 

1^'=  2(r  +  i-  g)  sin  -i  (F-a)cos-i 
(F  +  a)+/cosF  +  DN 


=  C^  +  "2-  f/)  (sin  F  -  sin  a)  +/  cos  F  +  DN  (68) 


154 


RAILROAD  ENGINEERING 


143 


If  the  lead  is  computed  for  a  turnout  from  a  straight  track 
using  a  No.  9  frog,  a  straight  point  rail  and  frog  rail  of  the  dimen- 
sions given  in  the  middle  section  of  Table  III*,  it  will  be  found 
that  the  lead  becomes  72.61  instead  of  84.75,  the  corresponding 
dimension  assuming  that  the 
lead  rails  were  circular  through- 
out. Table  III*  was  computed 
on  the  basis  of  the  above  equa- 
tions and  the  point  switch  di- 
mensions which  are  in  general 
use.  The  two  references  to  sec- 
tion numbers  in  the  table  are  to 
se(^tions  in  Webb's  "Railroad 
Construction,"  from  which  the 
tables  were  taken. 

121.  Turnout  from  the 
Outer  5ide  of  a  Curved  Track. 
the  dimensions  of  a  turnout,  from  a  curved  track  on  the  basis  of 
using  straight  point  rails  and  straight  frog  rails,  it  not  only  renders 
the  demonstration  exceedingly  complicated,  but  it  would  involve 
assumptions  regarding  the  mechanical  construction  which  probably 
would  not  be  followed  in  practice.  Therefore  the  following  dem- 
onstration is  given  with  the  purpose  of  showing  the  effect  on  the 


Fig.  121. 
When  it  is  attempted  to  compute 


Fig.  122. 

switch  dimensions  of  curving  the  main  track,  the  switch  rails  being 
circular  throughout,  and  then  drawing  a  reasonable  inference  as  to 
the  dimensions  which  should  be  followed  for  point  switches  from  a 
curved  main  track.     In  the  triangle  FCD,  in  Fig.  122,  we  have 

*See  Webb's  "Trigonometric  Tables,"  published  by  American  School  of  Corresjwnd- 

ftTiffi.  Phina.P-n   Til.     'Pricfi.  TtOc  1  kc 


144  RAILROAD  ENGINEERING 

(FC+CD) :  (FC-CD) :  :  tan^  (FDC+DFC) :  tan^(FDC  -DFC); 

but  \  (FDC  +  DFC)  =  90°  -  -i-  Q,  and  4"  (FDC  -  DFC)  =  ~  F; 
also  FC+CD  =  2R  and  FC-CD=^; 

.-.  2R  :  </  : :  cot  -^  ^  :  tan     -^-  F 

It.  1     .1 

:  :  cot  -^  1^   :  tan  -^  cr 

...  tan  -^  (9  =  -^  (69) 

Also,         OF  :  FC  :  :  sin  (9  :  sin  </>;      but  <^  =  (F  -  (9) 


then 


1  /t.    ,     1     \       sin  (9  ,      . 


The  lead,         BF  =  L  -  2  (r  +  4"  ^)  ^^^^  4^  '^         (^0 

A  study  of  the  three  equations  above  will  show  that  as  the 
curvature  of  the  main  track  increases  and  R  grows  less,  tan  6 
increases  and  ^increases.  Then  (F  -  6)  decreases  and  r  increases. 
When  Q  =  F,  as  it  readily  may,  (F  -  ^)  =  0  and  r  becomes  infin- 
ity,  that  is,  the  switch  rails  become  straight.  If  6  becomes  greater 
than  F,  sin  (F  -  6)  becomes  negative  and  /'  becomes  negative. 
The  interpretation  of  this  is  that  the  center  of  the  switch  track  will 
be  on  the  same  side  as  the  center  of  the  main  track.  The  figure 
will  then  correspond  with  Fig.  123  except  that  the  positions  of  O 
and  C  and  also  of  <^  and  6  will  be  transposed  and  also  that  "  main 
track"  should  read  "side  track."  Equations  73  and  75  will  be 
the  same  as  before,  but  equation  74  will  be  changed  to 

If  we  call  d  the  degree  of  curve  corresponding  to  the  radius  r, 
D  the  degree  of  curve  corresponding  to  the  radius  R,  and  d^  the 
degree  of  curve  of  a  turnout  from  a  straight  track  for  the  same 
frog  angle  F,  it  will  be  found  that  d  ==d'  -D  very  nearly.     It 


RAILROAD  ENGINEERING  145 

will  also  be  found  that  the  "  lead  "  as  computed  above  and  as  com. 
puted  for  a  straight  track  will  agree  to  within  a  few  inches  and 
frequently  to  within  a  fraction  of  an  inch. 

Example.  Compute  from  the  above  equations  the  values  of 
L  and  r  (and  then  of  d)  for  the  cases  when  the  main  track  has  a 
4°  degree  curve  and  when  it  has  a  10°  curve;  solve  them  for  num- 
ber 6,  9  and  12  frogs.  This  makes  six  cases.  Compare  them  with 
values  computed  by  the  approximate  rule. 

In  all  these  cases  it  may  be  shown  that  the  discrepancies  are 
very  small.  If  such  calculations  are  made  for  very  sharp  curves 
and  for  very  large  frog  angles  (which  must  be  considered  as  bad 
practice),  the  discrepancies  would  be  considerable,  but  since  such 
turnouts  (if  ever  made)  should  be  operated  at  very  slow  speeds,  the 
errors  would  have  but  little  practical  importance.  Therefore  we 
are  justified  in  applying  the  approximate  rule  for  turnouts  from  a 
curved  track — use  the  same  "lead  "  as  for  straight  track;  the  de- 
gree of  curvature  for  the  switch  rails  to  the  outside  of  the  main 
track  will  be  the  difference  of  the  degree  of  curve  for  the  main 
track  and  the  tabular  value  for  the  degree  of  curve  of  the  switch 
rails;  for  a  turnout  to  the  inside  of  a  curved  main  track  it  may  be 
similarly  shown  that  the  proper  degree  of  curve  for  the  switch 
rails  is  the  suirt  of  the  degrees  for  the  main  track  and  the  tabular 
value  for  the  switch  rails  from  a  straight  track. 

Also,  since  it  may  be  shown  that  the  effect  of  using  straight 
point  rails  and  straight  frog  rails  is  to  shorten  the  lead  and  to  lessen 
the  radius  in  approximately  the  same  proportion,  it  may  be  assumed 
without  material  error  that  we  may  apply  the  same  rule 'as  above, 
and  instead  of  taking  the  values  of  "  lead  "  and  ''  degree  of  curve  " 
for  the  switch  rails  from  the  tabular  form  which  uses  circular 
switch  rails  throughout,  we  may  take  them  from  the  revised  form 
using  straight  switch  rails  and  straight  frog  rails  and  apply  the 
same  rule. 

122.  Turnout  from  the  Inner  Side  of  a  Curved  Track.  By 
the  formation  of  precisely  similar  equations  as  were  used  in  the 
previous  section,  we  may  derive  the  equation 

tan^e  =  ^  (73) 


146 


RAILROAD  ENGINEERING 


From  the  triangle  OFC  we  may  derive 
OF  :  FC  ::  sin  (9  :  sin  (F  +  0\  from  which 
(.+  |,)  =  (R-i-,) 


sin  6 


The  lead  BF  =  L 


sin  (F  +  ^)      ^'^'^^ 
2  (ll  -  4  ^)  ''''  i  ^     ^75) 


The  details  of  the  solution  of  the 
above  equations  should  be  worked  out 
by  the  student;  also  a  numerical  dem- 
onstration of  the  fact,  already  referred 
to,  that  the  degree  of  the  turnout  [d) 
is  very  nearly  the  sum  of  the  degree 
of  the  main  track  (D)  and  the  degree 
[d')  of  a  turnout  from  a  straight 
track  when  the  frog  angle  is  the  same. 
It  will  be  found  that  the  discrepancy 
in  these  cases  is  somewhat  larger  than 
in  the  previous  case,  although  it  is  still  so  small  that  it  may  be 
neglected  when  the  curvature  of  the  main  track  is  small.  An  in- 
spection of  the  figure  will  show  that  when  the  curvature  of  the 
main  track  is  sharp  the  curvature  of  the  turnout  is  very  excessive. 
Such  conditions  should 
be  avoided  if  possible, 
that  is,  a  turnout  should  o'^-'^lf 
not  be  located  on  the  in-  "*-^^ 

side  of  a  very  sharply  ''^^^^ 

curved  main  track  if  it 
can  be  avoided. 

123.     Numerical 

Examples.      1.     Deter-  tJ ^-"- 

mine  the  lead  and  the  ra- 
dius of  curvature  for  a  Fig.  124. 
turnout  to  the  outside  of 
a  4°  30'  curve  using  a  No.  8  frog  and  a  point  switch. 

2.  Determine  the  lead  and  the  radius  of  a  curvature  for  a 
turnout  to  the  inside  of  a  3°  40'  curve  using  a  No.  7  frog  and 
point  switch. 


RAILROAD  ENGINEERING 


147 


In  each  of  the  above  examples  use  the  switch  point  angles, 
length  of  switch  point  and  length  of  straight  frog  rails  as  given  in 
Table  III*. 

124.  Connecting  Curve  from  a  Straight  Track.  The  "con- 
necting curve  "  is  that  part  of  the  siding  between  the  frog  and  the 
point  where  the  siding  becomes  parallel  with  the  main  track,  or 
the  distance  FS  in  Fig.  124.  Call  d  the  distance  between  track 
centers.  The  angle  FO,R  must  equal  the  angle  F.  If  we  call  /•' 
the  radius  of  the  connecting  curve,  we  may  say 


(^'-4^) 


d 


vers 


FR 


0"-4O 


sin  F 


(76) 


(77) 


The  distance  FR  may  be  shortened  somewhat  by  the  method 
indicated  in  Fig.  129.  Theoretical  accuracy  would  apparently  re- 
quire that  we  should  consider  a  short  length  of  straight  track  at 
the  point  F.  The  effect  may  readily  be  shown  to  shorten  the 
radius  /  and  to  shorten  the  distance  FR  by  an  amount  exactly 
equal  to  the  length  of  the  straight 
frog  rail,  but  in  actual  track  laying 
such  a  procedure  might  be  consid- 
ered a  useless  retinement.  And 
therefore  in  this  case  as  well  as  in 
the  succeeding  similar  cases,  the 
effect  of  the  straight  frog  rail  will  be 
ignored.  It  should  likewise  be  noted 
that  the  figure  has  been  drawn  for 
simplicity  as  if  the  switch  rails  were 
circular.  But  since  the  point  O^  has 
no  connection  with  the  demonstra 
tion,  it  is  immaterial  what  is  the 
form  of  the  switch  rails  back  of  F. 
the  following  similar  demonstrations. 

125.  Connecting  Curve  from  a  Curved  Track  to  the 
Outside.  As  in  the  previous  case  the  only  required  quantities  are 
the  radius  r  of  the  connecting  curve  from  F  to  S,  Fig.  125,  which 

*See  Webb's  •'Trigonometric  Tables,"  published  by  American  School  of  Correspond- 


Pig.  125. 


This  same  remark  applies  to 


148 


RAILROAD  ENGINEERING 


must  be  determined  from  r  and  the  angle  </>  (=  F  +  "^/r).     From 
the  triangle  CSF  we  may  write 

CS  +  CF  :  CS  -  CF  : :  tan  -i  (CFS  +  CSF)  :  tan  -^  (CFS  -  CSF) 

but-2-(CFS  +  CSF)  =  90°  --2"^;  and  since  ehe  triangle  0,SF 

is  isosceles,  ~  (CFS  -  CSF)  =4-F. 

.-.  2R  +  <Z  :  ^  -  ^  ::  cot  -2"  -^  :  tan  -^  F 


::  cot  -^  F  :  tan  -^-^ 


tan  ^  ^ 


1   _  1 

_  2n  {d  -  g) 
~    2R  +  ^ 


from  which 

(78) 


From  the  triangle  CO,F  we  may  derive 

r  -  -j^  ^  :  R  +  —  ^  ::  sin  >F  :  sin  (F  +  ^) 


1  /t?    ,     1     \       sin  ^ 


(F  -f-  ^) 


(79) 


Also 


FS 


Fig.  126. 
and  finally  that 


126.    Connecting  Curve  from 
a  Curved  Track  to  the   Inside. 

^^  There  are  three  solutions  accord- 
ing as  F  is  greater  than,  equal  to, 
or  less  than  "^.  In  the  first  case, 
we  may  readily  deduce,  as  in  the 
previous  section,  from  the  tri- 
angle CFS  (see  Fig.  126)  that 

(2R-6Z)  :{d^g)  :;cot-^^ 
1 


; tan  -g-  F 


1  2n(d-~g) 


(81) 


RAILROAD  ENGINEERING 


149 


And  as  before,  in  equations  78  and  79,  we  may  derive 

(„4,)=(„_J.,);,J^  (82) 

and  FS  =  2  (r-  ^  ^  )sin  -i-  (F  -  f )  (83) 

When  yjr  =1  Y,  equation  80  will  become 


tan 


1    ^  1         27i(d-g)  ^ 

Y  =  ^^  =     Q-^ — -j^  from  which  we  may  derive 

2R-d 


2n  2R 

4.n^  {d  -  g) 

This  equation  gives  the  value  of  R 
which  makes  this  condition  possible. 
If  we  make  F  =  "^  in  equations  81 
and  82,  we  find  in  the  first  case  that 
/'  is  infinite,  which  means  that  the 
track  is  straight,  and  in  the  second 
case  that  FS  =  infinity  times  zero, 
which  is  "indeterminate."  But  from 
the  figure  itself  we  may  readily  see 
that 

FS  =(E--^^/)sin^    (85) 


(84) 


Fig.  127. 


Also 


When  F  <  "^  we  may  derive  the  value  of  tan  -^  "^  to  be  the 

the  same  algebraically  as  in 
Equation  81,  although  the 
figure  is  so  different.  By  the 
same  method  as  before  we 
may  derive  for  the  value  of  r 
the  equation. 

Fig.  128.  gin  (^  -  F)        \°^^ 

FS  =  2  (r  +  i-  J,)  sin  4  (^  -  F)  (87) 


150 


RAILROAD  ENGINEERING 


127.     Crossover  Between  Two  Parallel  Straight  Tracks.    As 

in  the  previous  cases,  although  the  figures  are  drawn  for  simplicity 
with    switch    rails    as    simple    curves,    the    demonstrations    only 

involve  the  frog  angles  and  the  na- 
ture of  the  track  beyond  the  frog. 
The  better  method  is  that  shown  by 
the  full  lines,  when  the  track  is 
straight  between  the  frogs.  But 
this  consumes  so  much  of  the  main 
track  (many  times  what  is  indicated 
in  the  distorted  figure)  that  a  re- 
versed curve  (as  is  indicated  by  the 
dotted  curves)  may  be  used.  The 
length  of  the  straight  crossover  track 
is  RT. 


F,T  sin  F,  +  y  cos  F,  =  d 
d-g 


F,T 


sin 


g  cot  F, 


(88) 


The  total  distance  along  the  track  is 
DY  =  D,F,  +  YF,  +  FA  =  D,F,  +  XY  -  YF,  +  F,D, 
but  XY  =[d  -  g)  cot  F,  and  XF^  =  ^  -f-  sin  F, 

.-.  DV=D,F,+  {d  -g)  cot  F,- 

^^^+D.F,       (89) 

If  a  reversed  curve  with 
equal  frogs  is  used,  we  will 
have  the  construction  as  is 
indicated  by  the  dotted  lines, 
and  we  have 


vers  6  = 
also 


(90) 


Fig.  130. 


DQ  =  2/'sin6>     (91) 

If  it  should  for  any  reason  be  necessary  to  use  frogs  of  differ 
ent  sizes,  it  may  be  done,  but  the  point  of  reversed  curve,  instead 


162 


RAILROAD  ENGINEERING 


151 


of  being  in  the  exact  center,  will  be  as  is  indicated  in  Fig.  130. 
In  this  case  we  will  have 

/•j  vers    0   +  f\  vers  6  =  d 

.'.  vers  e  =  : —        (92) 

The  distance  along  the  track 
will  depend,  as  before,  on  the 
length  of  the  "lead"  for  each 
switch.  If  it  were  circular, 
as  indicated  in  the  figure,  we 
would  have 

B.N-C/', +n)sin^(93) 

but  the  true  lead  for  point 
switches  would  be  less  than 
this  by  the  difference  be- 
tween the  true  L  and  (/'  + 

-^g)  sin  F.    Therefore,  this  ^^' 

correction  should  be  computed  and  subtracted  for  each  switch. 

128.     Crossover  Between  Two  Parallel  Curved  Tracks.    In 

the  previous  case  there  is  no  practical  limitation  as  to  frog  num. 
bers,  but  in  this  case  there  are  limitations  on  what  frogs  are  per. 


Fig.  132. 

missible.  If  the  connecting  track  is  straight,  there  are  still  three 
cases  depending  on  the  value  of  F2,  as  in  section  121.  Two  of 
these  cases  are  illustrated  in  Figs.  131  and  132.     The  following 


152 


RAILROAD  ENGINEERING 


demonstrations  apply  to  both  figures.  If  one  frog  (F,)  is  chosen, 
then  F2  becomes  determined  as  a  function  of  F,.  If  Fj  is  the  angle 
for  some  even  frog  number,  F2  will  in  general  be  an  angle  that 
does  not  correspond  to  any  even  frog  number  and  therefore  will 
need  to  be  made  to  order.  If  F,  is  less  than  some  limit,  depending 
on  the  width  (^d)  between  the  parallel  tracks,  it  will  be  impossible 
to  have  a  straight  connecting  track,  and  at  some  other  limitation 
it  will  be  impossible  to  have  the  reversed  curve  connecting  track 
shown  later.  In  Figs.  131  and  132  assume  F^  as  known.  Then 
FiH  =  g  sec  Fp     In  the  triangle  HOFg  we  have 

sin  HF^O  :  sin  F,HO  :  :  HO  :  Yfi 

but  sin  F2HO  =  cos  F,  ;  RFfi  =  90°  +  F/,   sin  HF^O  =  cos  F/, 

HO  =  R  +  -i^-.~^-.^secF,;  F^O  =  R~~d  +^g 


hi^ 


.•.  cos  Fg  =  cos  F, 


-R  +-^d--^(/-(/seGF, 


^--^d  +-2(/ 


(94) 


Knowing  F^,  0^  is  determinable  from  equation  69.     To  determine 
the  relative  position  of  the  frogs  F,  and  F2, 

HOF2  =  180°  -  (90°  -  FJ  -  (90°  +  F,)  =  F,  -  F./,  then 
GF,  =  2  (R  Jr\d-\g)  sini-(F,  -  F^)  (95) 


RAILROAD  ENGINEERING  153 

If  the  connecting  curve  is  made  a  reversed  curve,  as  is  shown 
in  Fig.  133,  the  frogs  F,  and  F2  may  be  chosen  at  pleasure  (within 
rather  close  limitations,  however),  and  this  will  usually  permit  the 
adoption  of  regular  standard  sizes  and  will  not  necessitate  the  mak- 
ing to  order  of  special  sizes.  We  may  then  consider  that  F^  and 
F2  are  known  and  that  they  are  equal  or  unequal  as  desired.  Em- 
ploying formula  29  in  Table  XXX,*  we  may  write: 

2(S-0Q,)(S-00.) 
ve^sv-  ^()(^^^  ^^y^y^^ 

in  which  ^  ==  T  ^^^'  ^  ^^^^'  "^  ^^'  ^'^ 

but  OOi  =  R  +  -g-  ^  -  ^1 


.'.S=^  (2R  +  2r,)  =  R  -{-  r, 

S-00,  =  U  -{-  r,-R  -^-^d-r,=-^d', 

S-00,  =  R^r,-R-^d^r,  =  r,-{-r,-^d; 

d  {r,  +  r,-^d) 
...  vers  ^  =  J (96) 

{R-^d^r.^(K^^d-r) 

00  R  +  -g-  ^  -  r, 

sin  OO2  O,  =  sin  ^  ytit  =  sin       , (97) 

O,  O,  r,  +  7\       ^      ^ 

O2  O,  D  ==  ^  +  O,  O^  o  (98) 

NF,=.2(R--^.Z+  -|-^)sin4(^-  e,-0,)(99) 

The  chief  advantages  of  the  above  method  are  tliat  it  not  only 
permits  the  use  of  standard  size  frogs,  but  also  uses  up  less  of  the 
main  track  between  the  extreme  switch  points. 

*  Found  in  Webb's  "Railroad  Construction". 


154  RAILROAD  ENGINEERING 

129.  Problems  in  Switch  Computation.  1.  A  siding  runs 
off  from  a  straight  main  track,  using  a  No.  8.5  frog.  The  distance 
between  track  centers  is  18  feet.  What  is  the  radius  of  the  con- 
necting curve  and  its  length  ? 

2.  A  siding  using  a  No.  9  frog  runs  off  from  the  outside  of 
a  4°  30'  curve.  What  is  the  radius  and  length  of  the  connecting 
curve?  In  all  of  these  problems,  consider  the  distance  between 
track  centers  to  be  13  feet. 

3.  Using  the  same  frog,  a  siding  is  to  run  to  the  inside  of 
the  same  track.  What  will  be  the  radius  and  length  of  the  con- 
necting curve  ?  Until  "^  is  computed,  it  is  impossible  to  say  which 
of  the  three  possible  cases  w^ill  be  used,  but  the  solution  of  equation 
80  immediately  decides  that  point,  which  will  show  that  ^  is 
slightly  greater  than  F,  but  that  the  difference  is  so  little  that  the 

resulting  value  r  is  very  great.    -^  ("^  -  F)  is  such  a  small  angle 

that  Table  VI*  must  be  used  to  determine  its  sine. 

4.  If  a  crossover  is  to  be  ran  between  two  straight  parallel 
main  tracks  13  feet  between  centers,  using  No.  8  frogs,  how  much 
will  be  saved  in  distance  measured  along  the  main  track  by  using 
a  reversed  curve  rather  than  a  straight  track  ?  Since  the  dlffererK^e 
in*distance  is  called  for,  we  may  ignore  in  this  solution  the  abso- 
lute length  of  the  switch  rails  and  consider  that  they  would  be  the 
same  in  either  case. 

5.  Required  the  dimensions  for  a  cross-over  between  two 
main  tracks  which  are  on  a  4°  30'  curve;  the  distance  between 
track  centers  thirteen  feet,  the  frog  for  the  outer  main  track  (Fj  in 
Fig.  132)  is  No.  9;  Fg  is  No.  7;  the  connecting  curve  is  to  be  a 
reversed  curve.  When  the  radius  of  a  double  main  track  is  given, 
it  means  the  radius  of  the  center  line  between  the  two  tracks.  We 
must,  therefore  (as  indicated  in  Fig.  133),  add  and  subtract  6.5  to 
the  radius  of  a  4°  30'  curve  (1273.6)  to  obtain  the  radii  of  the 
centers  of  the  two  main  tracks.  The  figure  and  formulae  allow  for 
this.  Since  point  switches  would  unquestionably  be  used,  we 
must  determine  7\  and  n  by  the  method  outlined  in  §121;  Rj  the 
radius  of  the  outer  main  track  =  1280.1  (which  means  that  D,  = 
4°  29'),  while  R-g  ^^^  radius  of  the  inner  track  =  1267.1  and  D2  = 
4°  31'.     Then  by  the  rule  of  §121,  r,  =  radius  of  ((I,  +  D,)  °  curve 

*See  Webb's  "Trigonometric  Tables,"  pubUshed  by  American  School  of  Correspond- 
ence, Chicago.  111.    Price,  50c. 


RAILRAOD  ENGINEERING 


1.55 


=  radius  of  (7°  3X'  +  4°  29')  curve  =  478.34;  r^  =  radius  of 
[d^  -  D^)"  curve  =  radius  of  (12°  26'  -  4°  31')  curve  =  724.31. 
<i,  and  d^  are  the  degrees  of  curve  given  in  the  first  section  of 
Table  III*  as  being  suitable  for  a  No.  9  and  a  No.  7  frog  on  a 
straight  track.  Obtain  6^  and  0,,  by  substitution  in  equations  69 
and  73.  It  will  be  found  that  the  point  of  reversed  curve  comes 
but  a  fraction  of  an  inch  from  the  frog  point  Y^,  If  the  computa- 
tions had  apparently  indicated  that  the  point  of  reversed  curve 
\\X)uld  come  beyond  either  frog  point  (or  between  either  frog  and 
its  switch),  it  would  have  shown  the  impracticability  of  the  use  of 
a  No.  7  and  a  No.  9  frog  under  these  particular  conditions.  It 
shows  that  in  this  case  the  limit  was  practically  reached. 

6.  Solve  the  same  problem  using  a  No.  9  frog  in  both  cases. 
In  this  case  it  will  be  found  that  the  total  length  of  main  track 
between  the  extreme  switch  points 
will  be  somewhat  increased,  but 
that  the  point  of  reversed  curve 
will  be  nearly  midway  between 
the  two  tracks,  as  is  preferable. 
A.  comparison  of    the    two  solu-  ^^^ 

tions  will  then   show  how  close  ^^^    fh=A 

n  the  choice        ^-V-a    n/h MR  =|(F-a) 
t^ ■* — 1 —  — 


Fig.  134. 


are  the  limitations  ii 
of  frogs  to  be  used. 

i3o.  Practical  Rules  for 
Switch  Laying.  The  following 
directions  are  based  on  the  meth- 
ods previously  given  for  allow- 
ing for  the  eifect  of  straight  point  rails  and  straight  frog  rails 
when  used  from  a  curved  main  track.  When  the  position  of  the 
switch  block  is  definitely  determined,  then  there  is  no  choice  but 
to  cut  the  main  rails  wherever  the  location  calls  for,  but  as  the 
main  track  rail  would  be  merely  bent  out  to  form  the  outer  switch 
rail,  there  need  be  no  rail  cutting  near  the  switch  point,  except 
that  a  rail-joint  in  the  main  rail  should  not  come  at  or  near  the 
.:witch  point.  The  frog  has  a  length  of  from  six  to  nine  feet.  A 
movement  one  way  or  the  other  of  less  than  ten  or  twelve  feet  will 
bring  one  end  of  the  frog  at  an  existing  joint  and  thus  save  one 
fail  cutting. 

*See  Webb's  "Trigonometric  Tables,"  published  by  American  School  of  Correspond- 
ence, Chicago,  111.    Price,  50c?.  i  on 


156  RAILROAD  ENGINEERING 

After  having  definitely  determined  just  where  the  switch  is 
to  be  located,  mark  on  the  rails  the  points  B,  D  and  F  in  Fig.  134. 
Measure  off  the  length  of  the  switch  rails  DN,  and  locate  the  point 
M  at  the  distance  k  from  K.  If  the  frog  must  be  placed  during 
the  brief  period  between  the  running  times  of  trains  it  will  be 
easier  to  joint  up  to  the  frog  a  piece  of  rail  at  one  or  both  ends  of 
just  such  a  length  that  they  may  be  quickly  substituted  for  an 
equal  length  of  rail  taken  out  of  the  track.  When  the  frog  is  thus 
in  place,  the  point  H  becomes  located.  The  curve  between  M  and 
H  is  a  curve  of  known  radius.  Substituting  in  equation  54  the 
value  of  chord  and  R,  we  obtain  a?,  or  dh  in  Fig.  135,  which  is  the 
ordinate  for  the  middle  point  of  the  curve.  Then  a"  a  and  &'  c 
will  be  three-fourths  of  dh.  Theoretically  this  will  give 
a  parabolic  curve,  but  the  difference  will  not  be  appre- 
ciable. Having  located  and  spiked  down  the  rail  HM, 
the  opposite  rail  may  be  easily  put  in  at  the  proper 
gauge. 

Example.  Locating  a  switch  on  a  curved  main 
track.  Given  a  main  track  having  a  4°  30'  curve,  to 
locate  a  turnout  to  the  outside  using  a  No.  9  frog;  gauge, 
4  ft.  8i  in.;  /=6.00';  k  =  5l  in.;  DM  =  16.5  ft.;  and 
a  =  l°  44'  11".  Then  for  a  straight  track  r  would  = 
616.27  ((Z  =  9°18'  27").  For  the  curved  track  d  should 
Fig.  135.  be  nearly  (9°  18'-4°  30')  =4°  18',  or  r  =  1194.0.  L  for 
the  straight  track  would  be  72.61,  but  since  the  lead  is 
slightly  increased  (say  about  0.1 — see  §  121)  we  may  call  the  lead 
72.7,  although  this  difference  would  be  absolutely  imperceptible 
after  the  track  was  laid,  so  far  as  train  running  was  concerned. 
After  locating  the  switch  and  frog  point  as  described  above,  the 
frog  and  the  switch  rails  should  be  placed.  The  closure  for  the 
curved  rail  is  given  in  Table  III  as  42.92  and  curving  the  main  track 
would  make  it  slightly  longer  still,  say  43.0.  R  =  1194.0+2.35  = 
1196.35.  Applying  equation  55,  we  have  a: = 43.02^(8X1 196.35) 
=0.193,  the  ordinate  at  the  middle  point.  The  ordinate  at  each 
quarter  point  is  three-fourths  of  the  ordinate  at  the  center,  or,  in 
this  case,  0.145. 

131.    Slip  Switches.     The  complicated  demands  for  switch- 
ing in  yards  and  terminals  have  been  greatly  assisted  by  the  device 


RAILROAD  ENGINEERING 


157 


Fig.  13& 


Slip  Switches. 


Fig.  137. 


158 


KAILROAD  ENGINEERING 


known  as  slip  switches,  illustrations  of  which  are  shown  in  Figs. 
186  and  137.  Fig.  136  shows  a  "single  slip  "  in  which  the  two 
middle  frogs  are  fixed,  although  the  system  of  movable  frogs  illus- 


Section  A    B  Seccion    C  D 

Fig.  138.    Crossing. 

trated  in  Fig.  137  is  especially  applicable.  The  double  slip  switch 
illustrated  in  Fig.  137  makes  it  possible  for  a  train  coming  on  either 
track  to  run  directly  on  to  either  of  the  opposing  lines.  It  should 
be  noted  that  the  mechanism  is  made  inter- 
locking so  that  the  setting  of  a  switch  at  one 
end  will  simultaneously  set  the  switch  at  the 
other  end  as  is  required. 

132.  Crossings.  When  two  railroads 
cross  each  other  or  even  when  it  is  desired 
to  have  one  line  cross  another  without  having 
any  switch  connection,  a  crossing  may  be 
used.  If  the  angle  should  be  small  (which  is 
very  undesirable)  the  method  of  movable  frogs, 
shown  by  the  crossing  of  the  inner  main  rails 
of  Fig.  137,  may  be  used.  But  the  lines 
should  be  required  to  cross  each  other  as  nearly 
at  right  angles  as  possible  and  then  a  bolted  or  riveted  set  of 
frogs,  with  fillers  between  the  rails,  such  as  is  illustrated  in  Fig. 


Fig.  139. 


170 


RAILROAD  ENGINEERING 


159 


138,  may  be  used.  In  general  these  crossings  will  need  to  be 
made  to  order  according  to  the  angle  between  the  two  lines. 
Since  such  crossings  are  sometimes  operated  at  very  high  speeds 
the  construction  must  be  especially  strong  and  rigid.  When  both 
tracks  are  straight  the  frog  angles  are  identical,  or  more  strictly, 
two  of  them  are  "complements"  of  the  other  two.  When  one  or 
both  tracks  are  curved,  all  four  frogs  will  be  different  and  the 
computation  of  their  exact  value  becomes  a  somewhat  complicated 
geometrical  problem.  The  mechanical  construction  need  not  be 
essentially  different  from  that  shown  in  Fig.  138. 

i33.  Crossing.  One  straight  and  one  curved  track.  In 
Fig.  139,  R  is  known  and  also  the  angle  M,  made  by  the  center 
lines  at  their  point  of  intersection. 

M  zrz  NCM  and  NC  =  R  cos  M 
then  (R  -  i-  ^)  cos  F,  =  NC  +  -|-  ^ 


, .  JOS  F,  — 


R  cos  M  -f-  ~^(j 


Similarly  it  may  be  proved  that 


cos  Fg  = 


cos  F,  = 


cos  F^ 


R  cos  M  +  -^  ^ 

R  +  4.^ 


R  cos  M  -  -^  y 


R  + 


R  cos  M ^g 


R 


1 


(100) 


To  find  the  relative  positions  on  the  tracks  of  the  frogs,  we  may 
write 


171 


160 


RAILROAD  ENGINEERING 


F,P.  =  (r  +  i-^)8in  F,  _(r  -^!/)sm  F. 

HF.  =  (E-i^)(8inF.-8inF,) 

F,F,  =  (r  +  4^)  sin  F,  -(r  -  —  </)  sin  F, 


(101) 


It  should  be  noted  that  FgF^  will  not  be  exactly  equal  to  FjF^  al. 

though  the  difference  will  be  very  small. 

134.  Crossing.  .Both  tracks  curved.  The  angle  of  the  tan- 
gents (or  radii)  at  their  point  of  inter- 
section is  a  known  quantity  (M)  and 
also  the  two  radii  R,  and  1^^.  But 
since  we  must  deal  directly  with  the 
radii  of  the  inner  and  outer  rails  of  both 
curves,  it  will  be  easier  to  immediately 

\  ^\u/^)^^^^  \  add  (or  subtract)-^  g  to  Rj  or  E^  and 

"^    III     /    ^\^A  \  4>     '  ~ 

\  III  /^^        ^•^        thus  obtain  /',,  y\„  r.^,  and  /'^,  as  indicated 

\i/       ^--'''*  in  "Fimirfi  140       T^pfprrinor  in  thp  frianorlp 


Fig.  140. 


vers  F, 


in  Figure  140.    Referring  to  the  triangle 
F1C1C2,  and  calling  s^  =  ~^{c  ^  r^-\-  rj, 


we  may  write : 

2  (^i-^'OG'^i -^4) 


Similarly  in  the  triangle  Ffifi^^  let  s.^  =  -^  (c  -{-  r^  -\-  r^ 

and  in  the  triangle  FgCjCg,  let  ^g  =  -^  (<?  -f-  r^  -\-  r^ 

and  in  the  triangle  F^CjCg,  let  s^  =  -15- (6*  +  r^  +  r.^ 
and  then  we  may  write 


vers  F, 


vers  Fo 


vers 


2  («2-n)(^2-^) 


2 

(^3- 

-  ^0  (^3  - 

-n) 

2 

{^r 

r,r^ 
-  ^2)  (^4  - 

-n) 

(102) 


172 


RAILROAD  ENGINEERING  161 

To  determine  the  length  of  track  between  the  frogs  we  may  write 
sin  CjCaF^  =  sin  F^— ^ 

and  sin  C,C2F2  =  sin  Fg— ^ 

.-.  FAF,  -  CAF,  -  C.C.F,      (103) 

Knowing  the  angle  FoC2F^  we  readily  determine  that  the  chord 

F.^F^  =  2/\  sin  -^  (F2C2FJ.      In    a  precisely   similar  manner   the 

chords  FjFg,  FjFg,  and  FyF^  may  be  computed.  As  a  check,  it  should 
be  found  that  all  these  chords  are  nearly  although  not  quite  equal, 
likewise  the  mean  of  all  the  four  frog  angles  should  be  within  a 
few  seconds  of  the  value  of  M. 

135.  Examples.  1.  Determine  the  dimensions  and  the  frog 
fugles  for  the  crossing  of  a  straight  track  with  a  track  of  4°  curv- 
f.ture  (as  in  Fig.  135)  when  the  angle  M  =  72°  18'. 

2.  A  2°  curve  crosses  a  4°  curve  as  in  Fig.  140,  the  angle  M 
being  52°  20'.  Determine  the  frog  angles  and  the  chord  lengths 
between  the  frogs. 

YARDS  AND  TERMINALS. 

136.  Value  of  a  Proper  Design.  When  a  freight  train  arrives 
at  a  terminal  yard,  which  is  generally  in  a  city  of  considerable  size, 
with  one  or  more  other  railroads  or  branches,  the  train  load  will  in 
general  be  made  up  of  some  cars  which  will  need  to  be  shifted  to 
some  other  road  or  division  or  to  be  shunted  on  to  a  siding  where 
they  may  be  unloaded.  If  the  character  of  the  train  is  mixed, 
partly  coal  and  partly  general  merchandise  or  grain,  the  coal  cars 
must  be  sent  to  their  own  tracks  and  the  merchandise  to  theirs. 
A  "division"  point  of  a  road  is  frequently  the  terminus  of  one  or 
more  branches  as  well  as  the  point  where  freight  trains  are  perhaps 
made  up  anew,  especially  if  the  ruling  grade  on  adjacent  divisions 
is  so  different  that  the  train  load  which  can  be  hauled  by  one  engine 
is  very  different  on  the  several  divisions. 

A  little  study  of  these  facts,  together  with  others  which  will 
readily  suggest  themselves  in  this  connection,  will  show  the  vast 
amount  of  work  which  is  necessary  in  sorting  out  the  cars  in  a  yard. 

173 


162  RAILROAD  ENQINEERING 

Often  the  road  engine  is  cut  off  from  the  train  as  soon  as  it  has 
brought  it  to  its  proper  place  in  the  yard,  and  the  distributing  is 
done  entirely  by  switching  engines.  But  the  work  in  large  yards 
is  so  great  that  several  engines  will  be  required  for  the  work.  The 
cost  of  running  a  switching  engine  per  day  may  be  figured  as 
approximately  $25.  If  the  design  of  a  yard  can  be  so  altered 
that  one  engine  can  be  dispensed  with,  or  that  three  engines  may 
be  made  to  do  the  work  which  formerly  required  four,  we  would 
have  in  313  working  days  per  year  an  annual  saving  of  $7,825, 
which  capitalized  at  5%,  gives  |156,500  which  is  sufficient  to 
reconstruct  almost  any  yard. 

As  will  be  developed  later,  such  a  saving  is  by  no  means  an 
impossibility.  The  requirements  for  space  for  water  stations,  ash- 
pits,  coaling  stations,  turntables,  sand  and  oil  houses,  engine  houses, 
etc.,  and  their  proper  arrangement  so  as  to  avoid  useless  running  of 
the  engines,  is  another  feature  which  shows  the  value  of  a  system- 
atic design  for  a  yard.  When  a  yard  is  being  constructed  at  a  new 
place,  it  may  be  designed  on  the  basis  of  subsequent  work,  no  matter 
how  little  of  it  is  immediately  constructed,  but  very  many  yards 
were  laid  out  when  the  now  recognized  principles  were  unknown. 
Subsequent  additions  have  only  made  a  bad  matter  worse  until  it 
is  seen  that  an  entire  re-construction  is  necessary  to  make  the  yard 
what  it  should  be. 

137.  Freight  Yards.  General  Principles.  A  yard  built  on 
an  ideal  plan  is  in  general  an  impossibility.  Topographical  con- 
siderations usually  influence  the  problem  to  such  an  extent  that  the 
only  method  is  to  study  the  location  so  that  certain  fundamental 
principles  may  be  applied. 

1.  A  yard  is  a  classifying  machine  for  receiving,  sorting  and 
despatching  cars  to  their  several  destinations  as  rapidly  as  possible. 
Its  efficiency  is  measured  by  the  rapidity  with  which  it  accom- 
plishes this  and  the  economy  of  motive  power  which  is  required. 

2.  At  a  yard  which  is  the  terminal  of  a  division  the  freight 
trains  are  pulled  in  to  a  "receiving  track"  so  as  to  get  them  out  of 
the  way  and  off  of  the  main  track.  The  road  engine  is  then  run 
off  to  the  engine  yard  where  it  is  cleared  of  ashes,  loaded  with 
water,  coal,  sand,  etc.,  and  otherwise  prepared  for  its  next  trip. 
Perhaps  the  caboose  is  run  off  to  a  "caboose  track"  the  location  of 

174 


RAILROAD  ENGINEERING 


163 


which  is  made  convenient.  Then, 
if  the  train  is  a  "through  "  freight, 
another  engine  and  caboose  may  be 
attached  and  it  may  proceed  un- 
broken unless  a  change  in  ruling 
grade  requires  a  different  train  load. 

3.  There  are  certain  tracks  in 
a  yard  which  may  be  considered  the 
skeleton  of  the  yard.  On  these 
tracks  no  trains  should  be  allowed 
to  stand  except  temporarily.  Such 
tracks,  shown  in  Fig.  141,  in  which 
each  pair  of  rails  is  indicated  by  a 
single  line,  are  called  "  ladder  tracks," 
and  from  these  the  storage  tracks 
are  run  in  parallel  lines.  Other 
through  tracks  are  indicated  on  the 
plan. 

4.  The  storage  tracks  should 
usually  be  made  double-ended  or 
with  a  ladder  track  at  each  end. 
This  usually  facilitates  the  switching 
by  permitting  one  or  more  cars  to  be 
drawn  from  either  end  without  dis- 
turbing the  cars  at  the  other  end  of 
that  track. 

5.  In  recent  years  many  yards 
have  been  made  by  creating  an  arti- 
ficial hump  at  such  a  place  that  the 
grade  from  the  ladder  tracks  on  to 
the  storage  tracks  is  about  0.5  per 
cent.  This  creates  a  gravity  force 
of  10  pounds  per  ton  which  is  suf- 
ficient to  cause  a  car  to  roll  by  gravity 
from  the  ladder  track  on  to  any  stor- 
age track  to  which  it  may  be  di- 
rected. In  this  way  a  train  of  cars 
on  the  ladder  track  may  be  distrib- 


? 


3ll 


164 


RAILROAD  ENGINEERING 


uted  to  the  various  storage  tracks  with  great  rapidity.     Incident- 
ally there  is  no  dnicrer  of  a  car  running  out  from  the  storage  track 

on  to  the  ladder  track.  Symmetry  and 
economy  of  space  will  usually  require  that 
the  frogs  and  the  switch  dimensions  of  the 
switches  running  off  from  the  ladder  tracks 
shall  be  uniform.  No.  7  frogs  are  very 
commonly  used;  frogs  with  a  larger  frog 
number  make  an  easier  riding  track,  but 
they  require  more  space,  and  limit  the 
space  which  may  be  used  for  storage.  No. 
0  and  even  No.  5  frogs  are  sometimes  used 
on  account  of  the  economy  of  space  which 
is  thereby  obtained,  but  it  makes  harder 
rolling  and  greater  danger  of  derailment. 
^  138.     Connection  of  Freight  Yard 

I     with  Main  Tracks.     As  a  general  princi- 
5     pie  the  main  tracks  should  be  as  clear  as 
I     possible  from  the  yard  tracks  so  that  pas- 
-      senger  trains  may  run  through  freely  at  any 
3     time  without  even  the  danger  of  a  collision 
ei      with  any  freight  cars  or  of  interfering  with 
"^     the  work  of  the  freight  yard.     This  prac- 
^      tically  means  that  there  should  be  no  cross- 
ing of  the  main  tracks  by  any  tracks  used 
in  yard  operations  and  that  the  connection 
should  be  only  where  it  is  desired  to  run 
from  the  main  tracks  on  to  the  receiving 
tracks  and  that  here  the  switches  should 
be  thoroughly  protected  by  signals.     The 
ideal   construction  is  to  have  (on  double 
track  roads)  all  opposing-  tracks  cross  over 
or  under  each  other  so  that  two  trains  will 
never  approach  the  same  point  of  track 
except  when  they  are  moving  in  the  same 
direction  and  then  the  danger  of  a  collision 
will  be  largely  averted.     The  receiving 
tracks  (or  similar  tracks)  should  be  utilized  as  "departing  tracks" 


176 


RAILROAD  ENGINEERING  165 

on  which  outgoing  freight  trains  may  wait  for  their  signal  to  start 
without  interfering  with  any  passenger  traffic  on  the  main  line 
tracks  or  any  shifting  work  in  the  yard. 

139.  Minor  Freight  Yards.  The  name  applies  to  the  local 
collecting  or  distributing  yards  which  are  located  in  parts  of  a 
great  city  where  the  freight  business  is  especially  large.  The  cars 
are  brought  to  these  yards  by  means  of  long  switches  or  by  means 
of  floats  when  the  yard  is  located  on  a  water  front.  The  special 
feature  of  these  yards  is  the  fact  that  since  they  are  always  located 
on  very  valuable  land,  great  ingenuity  is  required  to  utilize  the 
limited  space  to  the  greatest  advantage.  This  usually  requires 
excessively  sharp  curvature,  which  may  be  limited  by  the  fact  that 
car  couplers  will  not  permit  the  car  bodies  to  make  a  large  angle  with 
each  other.  The  shortest  permissible  radius  is  175  feet  and  even 
this  is  undesirable.  Radii  as  short  as  50  feet  have  been  used  in 
some  yards,  but  in  that  case  an  extension  coupling  bar  is  placed 
between  the  cars.  Yards  for  receiving  or  distributing  freight  should 
be  provided  with  team  tracks  which  are  made  stub-ended  and  which 
are  preferably  placed  in  pairs  with  a  sufficient  space  for  roadway 
between  each  pair. 

Figures  141  and  142  are  ideal  plans  which  were  submitted  to 
the  American  Railway  Engineering  and  Maintenance  of  Way  Asso- 
ciation at  its  meeting  in  March,  1902.  As  "  ideal"  plans,  it  is  not 
supposed  that  they  can  be  literally  adopted,  but  a  study  of  them 
will  show  their  general  conformity  with  the  principles  stated  above, 
and  also  will  be  suggestive  of  plans  adapted  to  the  local  conditions. 

i4o.  Freight  Yard  Accessories.  Track  scales.  These  are 
for  weighing  freight  cars  on  the  track.  When,  as  is  frequently 
the  case,  the  scales  are  located  on  a  much  used  track,  an  auxiliary 
pair  of  rails  is  laid  about  six  inches  from  the  scale  rails  and  con- 
nected with  them  by  a  split  rail  switch  at  a  suitable  distance  from 
each  end  of  the  scales.  One  auxiliary  rail  is  supported  on  the  side 
of  the  scale  pit  and  the  other  on  several  posts  which  run  through 
the  scale  table  floor.  It  has  been  found  practicable  to  weigh  a 
whole  train  load  even  in  motion  by  running  it  very  slowly  over  the 
scale  tracks  and  noting  the  scale  reading  for  each  car  when  it 
becomes  central  over  the  pit. 


166 


RAILROAD  ENGINEERING 


Cranes.  The  frequent  transportation  of  individual  loads 
weighing  many  tons  requires  the  use  of  some  sort  of  unloader, 
which  may  vary  from  the  temporary  "gin  pole"  to  a  traveling 
crane  which  strides  one  or  more  tracks  and  a  roadway,  and  which 
may  travel  on  rails  parallel  with  the  switch  tracks  and  also  has  a 
"  traveler "  which  runs  perpendicular  to  the  tracks.  The  double 
horizontal  motion  (as  well  as  the  vertical  motion)  permits  the 
loading  or  unloading  between  any  car  and  wagon  placed  within  its 
range.  While  their  use  is  somewhat  limited,  there  are  occasions 
when  they  are  almost  indispensable. 

i4i.  Engine  Yards.  The  ideal  position  for  the  engine  house 
with  its  accessories  is  in  the  center  of  the  yard,  as  is  shown  in  Fig. 


=^,11  I  I    ..      I    ^-    I  I  I  I  ^^^^ 


Longttudinol     Section    of    Pit 

Fig.  143, 

141.  The  accessories  of  an  engine  house  are  shown  in  the  ideal 
plan  of  Fig.  143.  The  plan  of  the  cinder  pit,  which  is  shown  in 
detail,  allows  for  a  pit  about  four  feet  deep  under  two  tracks  on 
which  the  engines  run,  and  into  w^hich  the  ashes  can  be  directly 
dumped.  These  tracks  are  each  side  of  a  depressed  track  which  is 
sunk  to  such  a  depth  that  the  sides  of  a  gondola  car  will  be  below 
the  bottom  of  the  ashpits  under  the  engine  tracks.  The  dumped 
ashes  can  therefore  be  very  easily  shoveled  into  the  car  in  the 
depressed  track. 


178 


RAILROAD  ENGINEERING  167 

Passenger  terminals  for  large  cities  are  structures  which 
demand  the  services  of  an  architect  rather  than  an  engineer.  The 
engineering  features  are  largely  those  of  elevating  or  depressing 
the  approaching  tracks  so  as  to  avoid  the  grade  crossing  of  city 
streets,  and  all  such  problems  must  be  solved  individually.  Those 
who  wish  to  study  the  subject  further  may  find  it  treated  very 
fully  in  "  Buildings  and  Structures  of  American  Railroads,"  by 
Walter  G.  Berg. 

SIGNALING. 

The  following  description  of  signaling  is  not  to  be  considered 
as  a  complete  course  on  the  subject  as  that  would  require  more 
space  than  may  here  be  devoted  to  it.  The  discussion  has  been 
condensed  to  such  fundamental  facts  as  every  railroad  engineer 
should  know.  The  development  of  the  science  has  been  so  rapid 
during  late  years  that  one  must  follow  current  engineering  litera- 
ture to  keep  abreast  with  the  progress  of  the  work.  A  student 
desiring  a  more  throrough  course  in  the  groundwork  of  the  sub- 
ject is  referred  to  '-  The  Block  System,"  by  B.  B.  Adams  (234 
pages),  as  well  as  to  similar  but  earlier  works  by  W.  H.  Elliot  and 
W.  L.  Derr. 

142.  Systems,  When  railroading  was  still  in  its  infancy 
but  traffic  had  so  increased  that  rear-end  collisions  on  double  track 
became  an  imminent  danger,  two  general  plans  were  suggested  and 
tried  to  guard  against  such  accidents — (a)  the  time  interval  system 
and  ib)  the  space  interval  system.  Although  some  traces  of  the 
first  system  are  still  to  be  found  in  train  order  systems  and  in 
operating  rules  and  time  tables,  it  has  been  found  inadequate  for 
the  operation  of  heavy  traffic.  When  trains  are  run  close  together, 
even  a  short  delay  becomes  a  source  of  danger,  which  is  only  par- 
tially obviated  by  vigilant  work  by  the  rear  flagman,  and  even  this 
safeguard  is  only  obtained  at  the  expense  of  further  delay  in  wait- 
ing for  the  flagman  to  return  to  the  train  after  the  cause  of  the 
delay  is  removed  and  the  train  is  able  to  proceed.  The  space  in- 
terval  system  has  therefore  become  the  basis  of  all  modern  systems. 

Considered  from  another  standpoint,  the  methods  of  handling 
trains  may  be  divided  into  two  general  classes —  {a)  the  telegraphic 
order  system,  in  which  men  at  different  parts  of  the  line  receive 

179 


168  ^  ATLROAD  ENGINEERING 

orders  by  telegraph  regarding  the  movements  of  trains  which  will 

soon  pass  them  and  who  communicate  these  orders  to  the  trainmen 

either  verbally  or  by  signal,  and  [b)  those  systems  under  which  the 

signals  at  any  point  are  controlled   by  mechanism  at 

1  adjacent  points.     The  fundamental  difference  between 

the  two  systems  is  that  in  the  first  case  a  blunder  by  any 
p.  one  of  several  men  may  cause  an  accident;  in  the  second 
case,  blunders  are,  to  a  considerable  extent,  mechanically 
impossible,  and  when  made  are  generally  immediately 
apparent  to  one  or  more  others,  and  may  be  corrected 
in  time  to  prevent  an  accident. 
®  The  first  system  includes  the  method  by  which  a 

large  proportion  of  the  trains  of  the  country  are  operated 
— the  "train  order"  system,  which  will  not  be  here  elab- 
orated since  "  signals  "  are  not  a  necessary  feature  of  it. 
©Under  this  method  the  train  crew  receive  their  orders, 
issued  by  the  train  despatcher  of  the  division,  which 
are  written  out  by  the  telegraph  operator  at  the  local 
office  where  received.  The  train  is  then  run  in  accord- 
ance with  such  orders  until  it  reaches  the  next  train 
4  ©  order  office.  The  first  system  also  includes  the  simple 
manual  system,  described  in  the  next  section.  The 
various  systems  of  controlling  the  signaling,  culminat- 
ing in  the  absolutely  automatic  system,  will  be  succes- 
I  sively  described. 

*  ®  143.     Simple  flanual  System.    In   this,  as  in  all 

other  block  systems,  the  road  is  divided  into  sections 
or  "  blocks  "  whose  lengths  are  varied  somewhat  to  suit 
the  method  adopted  and  the  natural  conditions,  and 
^  @  also  are  made  roughly  proportional  to  the  traffic.  For 
example,  on  the  main  line  of  the  Pennsylvania  Rail- 
H  road  between  Philadelphia  and  Harrisburg  the  sections 

Pig.  144.  have  an  average  length  of  a  little  over  two  miles,  a 
few  are  four  miles  long,  and  some  (especially  where  the 
suburban  traffic  is  heaviest)  are  less  than  one  mile  long.  On  the 
other  hand,  on  a  road  with  less  traffic  (although  sufficient  to  re- 
quire the  block  system),  the  blocks  might  have  a  much  greater 
leno-th.     ''  Absolute  "  blocking  forbids  the  entrance  of  a  train  into 


180 


RAILROAD  ENGINEERING  169 

a  block  until  the  preceding  train  has  passed  out  of  it.  This  prac- 
tically means  that  the  trains  must  average  considerably  over  one 
block  apart,  since  train  B  (see  Fig.  144)  cannot  enter  the  block 
(2 — 1)  until  train  A  has  passed  out  of  that  block,  and  the  fact  is 
telegraphed  back  so  that  the  signals  at  (2)  may  be  set  for  train  B 
to  enter  the  block.  Train  C  and  the  succeeding  trains  must  vir- 
tually maintain  the  same  interval  even  though  they  temporarily 
move  up  closer.  At  a  freight  train  speed  of  15  miles  per  hour, 
trains  could  be  run  through  blocks  five  miles  long  at  intervals  of 
twenty  minutes  plus  the  time  required  for  signaling  between  sta- 
tions and  for  the  trains  to  pass  by  the  signal  station.  Under  the  « 
simple  manual  system  the  rules  of  operation,  although  varied  in 
detail,  are  essentially  as  follows  for  double- track  work: 

When  train  A  has  passed  (1)  the  operator  there  telegraphs  the 
fact  back  to  (2),  and  then  the  operator  at  (2)  knows  that  the  block 
fro.n  (2)  to  (1)  is  clear  and  that  he  can  admit  train  B  to  the  block. 
If  train  B  does  not  arrive  at  (2)  for  some  time  afterward,  (2) 
should  obtain  definite  word  from  (1)  immediately  before  B  is  due 
that  the  block  is  clear,  since  it  might  have  become  obstructed  by 
switching  operations  or  otherw^ise.  As  soon  as  train  B  has  passed 
(2)  the  fact  is  telegraphed  back  to  (3),  which  informs  (3)  that  the 
block  (3 — 2)  is  clear.  The  method  of  communication  is  usually 
by  the  ordinary  Morse  alphabet,  but  since  the  facts  to  be  commu- 
nicated are  very  few  and  simple,  a  system  of  taps  on  electric  bells, 
which  can  be  more  easily  and  quickly  learned  than  the  Morse 
alphabet,  are  sometimes  used.  During  recent  years  even  the  tele- 
phone has  been  used  for  this  purpose.  Some  of  the  mechanical 
details  of  this  method  will  be  given  later.  Each  road  employing 
such  a  system  has  a  more  or  less  elaborate  set  of  rules  governing 
the  operation  of  the  signals,  whose  object  is  to  make  the  work  as 
mechanical  as  possible,  to  guard  against  giving  wrong  signals  and 
to  locate  the  blame  when  an  error  is  made. 

It  should  be  noted,  however,  that  there  is  nothing  to  prevent 
a  signalman  from  giving  a  "clear"  signal,  when  he  should  show 
a  "  stop  "  signal,  even  when  he  has  been  instructed  otherwise  and 
has  perhaps  reported  by  telegraph  that  he  has  obeyed  orders.  In 
short  he  is  not  "controlled,"  and  in  case  of  an  accident  there  is  a 


181 


170  RAILROAD  ENGINEERING 

question  of  veracity  between  him  and  the  engineman.  The  sys- 
tem has  the  merit  of  cheapness,  since  the  signals  may  be  of  the 
cheapest  form  and  the  intercommunication  may  be  done  by  the 
cheapest  form  of  telegraphic  circuit. 

Permissive  Blocking.  There  is  a  variation  of  the  "absolute" 
system  which  is  also  applicable  to  some  of  the  following  systems 
and  which  facilitates  traffic  although  at  some  sacrifice  of  safety. 
Under  this  system,  a  train  is  allowed  to  proceed  into  a  block  even 
though  there  is  a  train  still  there.  But  the  train  must  be  under 
"perfect  control"  (some  rules  limiting  the  speed  to  six  miles  per 
«  hour)  so  that  it  may  be  stopped  very  quickly  if  necessary.  By 
this  means,  the  delay  of  a  succeeding  train,  and  perhaps  of  several 
following  trains,  is  very  greatly  reduced.  Of  course  such  a  prac- 
tice requires  extreme  caution  to  avoid  accidents,  and  there  are  very 
minute  rules  to  be  followed  when  such  running  is  permitted  at  all. 

When  heavy  passenger  trains  are  run  at  a  speed  approaching 
60  miles  per  hour,  it  becomes  impracticable  to  make  a  "service" 
stop  much  within  1,500  feet.  Although  a  stop  viay  be  made  in  a 
much  shorter  distance,  it  induces  very  severe  strains  in  the  rolling 
stock  and  hence  should  be  avoided.  But  since  it  is  frequently 
impossible,  on  account  of  curves  or  other  obstructions,  to  see  sig- 
nals more  than  a  few  hundred  feet  away,  an  engineman  dare  not 
approach  a  "home"  signal  at  very  high  speed  for  fear  a  stalled 
train  may  be  immediately  beyond  it.  Therefore  a  "  distant  sig- 
nal^^"*  which  forewarns  the  engineman  of  the  indication  of  the 
"home"  signal,  is  placed  800  to  2,500  feet  from  the  home  signal. 
The  required  distance,  which  for  mechanical  reasons  is  made  as 
short  as  possible,  except  as  noted  below,  depends  on  the  grade  and 
on  how  far  from  the  signal  it  may  be  clearly  seen. 

When  the  distant  signal  is  set  for  "clear,"  the  engineman 
knows  that  he  may  proceed  at  least  as  far  as  the  second  home 
signal  ahead;  when  it  is  set  for  "  caution,"  he  knows  that  he  may 
proceed  at  least  as  far  as  the  next  home  signal,  but  he  must  expect 
to  be  stopped  there  and  he  must  have  his  train  under  such  control 
that  he  can  stop  there  if  required.  Sometimes  the  signal  becomes 
cleared  by  the  time  he  reaches  the  home  signal  and  there  is  no 
actual  delay  beyond  a  slight  reduction  in  speed,  but  the  indication 
of  the  distant  signal  enables  him  in  any  case  to  approach  the  home 

182 


RAILROAD  ENGINEERING 


171 


■-© 


signal  confidently,  knowing  beforehand  that  it  will  be  "clear"  if 
the  distant  signal  was  "  clear."  In  any  system  where  the  signal- 
ing is  "controlled,"  snch  a  distant  signal  is  locked  so  that  it  can- 
not indicate  clear  when  the  home  signal  indicates  stop.  Under 
the  "automatic"  systems  the  distant  signal  is  usually  placed  on 
the  same  post  as  the  home  signal  for  the  preceding  block.  In  this 
case,  when  the  distant  signal  indicates  clear,  the  engineman  knows 
that  his  road  is  clear  for  two  full  blocks,  but  he  may  have  to  slacken 
speed  when  he  reaches  the  next  block  station. 

144.  Controlled  Manual  System.  In  the  pre- 
vious system  the  only  connection  between  the  signal 
stations  is  the  telegraphic  communication  of  informa- 
tion. The  "controlled  manual"  system  includes  the 
following  essential  elements.  The  signals  at  each  sta- 
tion are  locked  by  electromagnets  which  are  controlled 
electrically  from  the  signal  station  ahead.  When  a 
train  approaches  (i),  (i)  must  notify  (^)  of  it.  If  the 
last  previous  train  has  passed  {2)  and  there  is  no  other 
impediment,  {2)  will  unlock  (^)'s  lever  electrically,  so 
that  it  is  possible  for  (i)  to  set  a  clear  signal.  After 
the  train  has  passed  (i),  the  signal  at  (i)  is  set  for 
the  "stop"  position.  It  will  then  be  impossible  for 
him  to  set  it  clear  again  until  permitted  to  by  (2). 
Knowing  that  the  train  is  coming,  (2)  inquires  of  (5)  if 
the  block  {2 — 3)  is  clear  and  if  so  (5)  will  unlock  (^)'s 
lever  so  that  it  can  be  set  for  clear.  The  above  is  the 
simplest  and  earliest  form  of  such  a  system. 

The  chief  advance  over  the  simple  manual  system 
lies  in  the  mutual  control  of  the  signal  offices  on  each 
other.  A  signalman  cannot  set  a  signal  clear  except  by 
the  action  of  the  next  signalman  ahead  who  thereby 
certifies  that  the  block  ahead  is  clear.  The  chances  of 
error  are  thereby  decreased.  The  electrical  control  is 
maintained  over  a  "wire  circuit,"  but  the  system  is 
made  much  more  under  control  by  adopting  features  Fig.  145. 
which  are  essentially  those  of  the  automatic  system. 
The  two  rails  of  the  track  are  carefully  insulated  from  each  other, 
and,  near  each  signal  station,  the  abutting  rails  are  insulated  at 


■■© 


-0 


183 


172 


RAILROAD  ENGINEERING 


b  6 


some  joint  by  joining  them  with  insulated  joints  such  as  are  de- 
scribed in  section  107. 

At  B,  Fig.  146,  a  track  battery  sends  a  current  through  the 
rails  wliicli  energizes  the  track  relay  at  A,  which  operates  the  sig- 
nal mechanism  at  A.  The  presence  of  even  a 
single  pair  of  wheels  on  the  track  between  A 
and  B,  or  even  on  the  siding  up  to  the  ''  fouling 
point,"  will  cause  the  current  to  be  short-cir- 
cuited and  it  will  fail  to  energize  the  relay  at  A. 
By  this  means  it  is  readily  arranged  that  when 
the  train  passes  A,  A's  signal  will  automatic- 
ally fall  to  "stop"  and  will  become  locked  there 
so  that  it  cannot  become  unlocked  until  the 
train  passes  the  insulated  joints  at  B.  When 
the  train  passes  B,  the  current  through  the  re- 
lay w\\\  then  become  strong  enough  to  release 
the  lock  and  then  A  can  set  his  signal  to  "  clear  " 
if  permitted  to  by  B. 

The  method  involves  both  a  wire  circuit 
and  a  track  circuit.  But  when  the  sections  are 
very  long,  it  becomes  very  difficult  to  control  the 
track  circuit  so  as  to  avoid  leakage  and  yet  give 
the  current  sufficient  strength  to  do  its  required 
work.  And  so  the  method  is  still  further  com- 
plicated by  eliminating  long  stretches  of  the 
^  §  track  circuit,  but  retaining  it  in  the  track  near 
(^~1^-^  each  signal  station  so  that  the  signals  wnll  be 
§j  automatically  operated  and  controlled  as  before. 
It  should  be  noted  that  if  a  car  was  stand- 
ing on  the  siding  and  was  moved  toward  the 
switch  point  by  wind,  or  through  malicious  mis- 
chief or  otherwise,  as  soon  as  it  passed  the  foul- 
ing point  the  signal  at  A  would  automatically 
go  to  ''stop"  and  the  signal  would  stay  locked  until  the  track  was 
cleared.  A  broken  rail  would  have  the  same  effect  of  locking  the 
signal  and  would  start  an  investigation  to  determine  the  trouble. 
145.  Automatic  Systems.  Some  of  the  principal  essentials 
of  the  automatic  systems  have  already  been  described  above.     Some 


\<\ 


Fig.  146. 


b 


<0 


184 


RAILROAD  ENGINEERING  173 

of  the  differences  are  as  follows.  The  mechanical  work  to  be  per 
formed  by  the  electric  current  in  the  controlled  manual  system  is 
limited  to  unlocking  certain  mechanisms  or  unlocking  the  signals 
so  that  by  gravity  they  will  assume  the  "stop"  position.  The  heavy 
work  of  moving  the  signals,  which  are  usually  of  the  "semaphore" 
type  (described  later)  is  performed  by  the  signalmen.  But  auto- 
matic signals  must  be  worked  by  a  mechanism  which  always  has 
sufficient  power  to  move  the  signals.  This  practically  means  that 
the  signals  must  have  such  a  form  and  be  so  worked  that  but  little 
force  will  be  required  to  move  them. 

The  earliest  forms  were  targets  mounted  on  a  vertical  axis 
which  was  swung  around  by  clockwork.  When  set  for  "  stop  "  a 
red  target  would  show;  when  set  for  "clear"  the  red  target  would 
turn  edgewise  and  a  white  target  of  different  form  which  was  previ- 
ously  edgewise  (or  perhaps  no  target  at  all)  would  then  show.  A 
lantern,  with  red  lenses  on  two  opposite  faces  and  white  (or  green) 
lenses  on  the  other  two  faces  would  be  set  on  top  of  the  axis.  A 
weight  moving  up  and  down  in  a  hollow  iron  post,  would  be  peri- 
odically wound  up  to  provide  the  power.  Each  time  the  signal  is 
changed  from  "stop"  to  "clear"  or  from  "clear"  to  "  stop"  the  axis 
turns  one-quarter  turn.  One  objection  to  the  method  lies  in  the 
fact  that  since  putting  even  a  handcar  or  a  track  gauge  on  the 
rails  will  turn  the  signal  to  danger  and  taking  it  off  will  restore  it 
to  clear,  the  mechanism  will  be  made  to  work  so  often  that  it  will 
require  rewinding  with  annoying  frequency  and  then  perhaps 
become  run  down  and  fail  to  work. 

To  guard  against  one  source  of  danger,  the  mechanism  is 
made  to  open  the  circuit  and  thus  put  the  signal  to  "stop"  just 
before  it  becomes  run  down,  so  as  to  avoid  the  possibility  of  the 
signal  indicating  clear  when  it  should  indicate  danger.  The  clock- 
work system  is  still  in  successful  use  on  some  of  the  systems  where 
it  has  been  installed  many  years,  but  the  more  recent  designs  use 
an  enclosed  disk  signal  (described  later).  An  important  detail  is 
the  placing  of  the  signal  200  feet  in  advance  of  the  entrance  of  a 
block  section.  This  enables  the  engineer  to  see  the  signals  turn  to 
danger  as  a  result  of  his  entering  the  block  and  he  thus  knows  that 
there  is  a  signal  protecting  him  until  he  reaches  the  next  signal. 


185 


174  RAILROAD  ENGINEERING 

If  the  signal  fails  to  work,  it  shows  that  there  is  something  wrong 
with  the  mechanism  and  he  will  take  precautions  accordingly. 

Another  advantage  of  tlie  track  circuit  system  lies  in  the  fact 
that  if  a  switch  be  opened  anywhere  in  a  block,  the  switch  being 
provided  with  a  circuit  breaker,  the  circuit  will  be  broken  and  the 
signal  will  automatically  fall  to  danger.  In  short,  almost  any  de- 
fect or  impediment  to  a  clear  track  will  be  indicated  by  the  signal. 
And  herein  lies  one  troublesome  feature:  the  circuit  is  so  sensitive 
that  any  accidental  short-circuiting  (even  though  not  due  to  any 
defect  or  obstruction  of  the  track)  will  delay  traffic.  The  opposite 
(and  far  more  serious)  error  in  operation — indicating  "  clear"  when 
it  should  indicate  "  stop" — will  only  be  caused  by  a  defect  in  the 
mechanism,  and  the  record  in  that  respect  is  very  good,  the  pro- 
portion  of  such  errors  to  number  of  signal  movements  being 
exceedingly  small. 

146.  Mechanical  Details.  The  train  order  system  does  not 
necessitate  signals  of  any  kind,  but  on  many  roads  which  make  no 
claim  to  a  block  signal  system  a  signal  of  some  sort  will  be  dis- 
played from  the  local  train -order  office.  The  signal  may  be  a  mere 
flag  on  a  stick;  an  improvement  is  to  hang  it  from  a  horizontal 
support,  the  lower  edge  being  weighted,  the  whole  being  provided 
with  a  cord  which  is  run  back  to  the  office,  which  permits  the  ready 
display  or  removal  of  the  flag.  Some  western  railroads  have  im- 
proved these  by  using  some  "home-made"  signals  operated  simi- 
larly,  but  using  a  target  made  of  thin  wood  or  of  sheet  r\etal. 
From  this  it  is  but  a  short  step  to  the  standard  "  semaphore,"  illus- 
trated  in  Fig.  147  and  elsewhere. 

The  semaphore  consists  essentially  of  a  board  about  ^ve  feet 
long,  eight  inches  wide  at  the  outer  end  and  six  inches  wide  at  the 
hinge  end.  The  hinge  is  a  somewhat  elabo^'ate  casting  with  one  or 
more  "  spectacles  "  as  holders  of  colored  glass  lenses.  Since  the 
weight  of  the  casting  on  the  spectacle  side  is  usually  not  sufficient 
to  overbalance  the  weight  of  the  semaphore  board,  a  counterweight 
is  so  attached  that  if  the  rods  or  wires  to  the  signal  cabin  should 
break,  the  signal  will  automatically  assume  the  horizontal  position, 
which  is  universally  considered  as  the  "  stop  "  or  '/  danger  "  signal. 
When  the  axis  of  the  board  passes  through  the  hinge  bolt,  as  is 

186 


RAILROAD  ENGINEERING 


175 


shown  in  Fig.  147,  the  "  clear  "  position  is  given  by  inclining  the 
board  at  an  angle  of  45°,  as  shown  in  position  B. 

Another  form  is  to  have  the 
board  eccentric  to  the  hinge,  so 
that  it  may  be  dropped  to  a  verti- 
cal position  and  still  show  outside 
of  the  post.  As  a  general  principle 
of  construction,  the  board  should 
be  clearly  visible  even  in  foggy 
weather,  and  therefore  the  board 
should  not  come  down  directly  in 
front  of  the  post,  for  in  foggy 
weather  it  would  not  be  clearly 
visible  and  an  engineman  might 
pass  the  signal  thinking  it  was  in 
front  of  the  post,  when  it  might 
have  been  broken  off  and  should 
have  indicated  danger.  Fig.  147 
shows  a  wooden  post;  the  latest 
high-grade  practice  now  uses  iron 
posts  with  suitable  castings  at  top 
and  bottom.  One  advantage  of 
such  posts  is  the  placing  of  the  rods 
inside  of  the  post  where  they  are 
less  subject  to  interference  from 
snow  and  sleet  and  from  malicious 
mischief. 

The  boards  are  always  set  so 
that  they  point  to  the  right  from 
the  track  which  they  govern,  or 
in  other  words  a  signal  which 
points  to  the  left  of  its  supporting 
pole,  as  seen  by  an  approaching 
v.^ain,  governs  trains  moving  in  the 
opposite  direction.  Sometimes  the 
boards  are  painted  red  on  the  gov-  ^.^  j,,    semaphore, 

erning  side  and  white  on  the  other 
side^  but  whatever  the  variation  in  practice  the  indication  is  inde- 


187 


176 


RAILROAD  ENGINEERING 


pendent  of  the  color,  and  on  some  roads  the  color  is  "neutral,'^  so 
as  to  emphasize  the  fact  that  the  engineman  must  be  governed  by 
\X\^  form  Siud  j)Ositio'fi  of  the  board  rather  than  by  the  color. 

The  only  essential  variation  of  form  of  the  blade  lies  in  mak- 
ing the  ends  of  all  home  signals  square  and  of  all  distant  signals 
notched  or  of  a  "fishtail "  form.    One  other  form  used  for  the  dis- 


Fig.  148. 

tant  signal  is  to  make  it  pointed.  When  there  are  but  two  tracks 
the  semaphores  are  usually  placed  on  separate  posts  on  each  side 
of  the  roadbed.  Even  when  there  are  four  tracks,  the  signals  for 
the  two  tracks  on  each  side  may  be  placed  on  one  main  pole  which 
has  a  cross-arm  and  two  uprights,  each  carrying  one  or  more  sema- 
phores, as  shown  in  Fig.  148.  But  when  there  are  more  than  four 
tracks  (as  in  yards),  and  frequently  on  four-track  roads,  the  signals 
are  carried  on  a  "  bridge  "  such  as  is  illustrated  in  Fig.  149.  In  such 
a  case  tiie  signals  for  each  track  are  placed  directly  over  the  track. 


188 


KAILROAD  ENGINEERING 


177 


189 


178  RAILROAD  ENGINEERING 

When  more  than  one  square-ended  signal  is  over  a  track,  the 
upper  one  refers  to  the  through  track  and  the  lower  ones  to 
the  switches  which  will  be  immediately  encountered.  Note  in 
Fig.  149  that  the  signal  bridge  in  the  background  has  boards  on 
the  left  side  of  the  posts  and  that  they  are  evidently  white.  This 
shows  that  the  bridge  governs  movements  toward  the  observer, 
while  the  signals  on  the  bridge  in  the  foreground  evidently  govern 
train  movements  in  the  direction  the  observer  is  looking.  The 
mechanism  of  all  such  signals  is  necessarily  somewhat  exposed, 
and  is  liable  to  be  actually  blocked  when  covered  with  snow  and 
sleet.  A  considerable  amount  of  power  must  therefore  be  available 
to  operate  such  signals. 

Another  form  in  extensive  use  is  the  enclosed  signal. 

Enclosed  signals.  There  are  two  great  arguments  for  and 
against  the  use  of  such  signals.  On  the  one  hand,  the  mechanism 
is  entirely  enclosed  and  protected  from  the  weather  and  is  therefore 
uninfluenced  by  wind,  snow  or  sleet.  Also  the  mechanism  can  be 
made  so  very  light  and  delicate  that  it  requires  only  a  small  per- 
centage  of  the  power  required  to  operate  semaphores,  and  therefore 
they  can  be  operated  by  an  electric  current  of  very  low  voltage. 
On  the  other  hand,  the  signal  is  not  one  oi  form  and  position  but 
of  color  only.  It  is  argued  that  it  cannot  be  as  clearly  seen  in 
stormy  weather  and  on  that  account  is  less  safe.  While  it  is  un- 
questionably true  that  the  signal  indication  is  less  visible  in  bad 
weather  than  a  semaphore,  yet  the  net  advantages  of  the  system 
are  such  that  the  system  is  very  largely  used. 

The  external  appearance  of  the  top  of  the  signal  (the  post 
being  omitted  in  the  illustration)  is  as  shown  in  Fig.  150.  "  Clear" 
is  indicated  by  the  disk  opening  showing  white.  To  indicate 
danger  a  very  light  screen,  made  by  stretching  red  silk  over  a  light 
hoop,  is  swung  over  the  opening.  At  night  the  lantern  on  the  rear 
side  shines  through  the  opening,  showing  white  or  red  according  to 
the  position  of  the  screen.  The  detail  of  the  mechanism,  shown 
in  Fig.  151,  explains  its  operation.  When  the  magnet  is  energized 
the  disk  is  drawn  up  out  of  view  and  the  signal  shows  white.  If 
the  current  fails  for  any  reason,  the  disk  falls  by  gravity  and  comes 
into  view.  The  power  required  is  so  small  that  the  magnet  not 
only  controls  the  signal  but  also  develops  the  power  to  move  it. 

190 


RAILROAD  ENGINEERING 


179 


147.  Wires  and  Pipes.  "Wires  are  used  for  the  transmission 
of  electric  current  and  pipes  are  used  to  transmit  pneumatic  pres- 
sure— as  discussed  later.     But  the  above  heading  refers  to  wires 


TUT  TtJT 

Fig.  150.    Enclosed  Signal. 

and  pipes  as  used  to  mechanically  transmit  motion  from  the  signal 
cabin  to  the  signal.  When  the  parts  may  be  made  to  work  by 
tension,  No.  9  wires  may  be  used.  When  it  is  required  to  turn  a 
right  angle  a  grooved  wheel  is  used  and  a  short  length  of  chain 


Fig.  151.    Hall  Automatic  Signal  Magnet. 

is  substituted, for  the  wire.  Sliorht  de- 
flection  for  pipes  is  accomplished  by  means 
of  a  sei-ies  of  bent  rods  running  through 
guides,  as  shown  in  Fig.  152.  If  the  de- 
flection is  greater,  each  rod  must  have  a 
"  bell  crank."     It  is  possible  to  work  a  sig- 

nal  with  one  wire,  depending  on  gravity  for  the  reverse  motion, 
but  good  practice  requires  a  wire  for  each  motion.     Signals  are 


191 


180 


RAILROAD  ENGINEERING 


sometimes  operated  mechanically  at  a  distance  of  2,000  feet  from 
the  cabin.  For  such,  wires  are  practically  a  necessity,  but  when 
the  signals  are  nearer,  pipes  which  may  exert  a  push  as  well  as  a 
pull  are  used. 

Comjpensators.     The   coefficient  of  expansion  of  iron  is  so 
high  that  the  change  of  length  in  a  wire  or  pipe  several  hundred 


Deflecting  ffocfs 


Bell  Crank 


Fig.  152. 


feet  long  is  so  great  that  the  signaling  mechanism  is  thrown  out 
of  adjustment  unless  there  is  some  automatic  device  to  counteract 
it.  The  change  of  length  of  1,500  feet  of  wire  due  to  a  fall  of 
temperature  from  100^  F.  to  20°  is  1500  X  80  X  .0000065  = 
0.78  foot  =  9.36  inches.  A  much  less  change  than  this  would 
require  adjustment.  The  geometrical 
principle  of  the  automatic  compensators  is 
shown  in  the  upper  part  of  Fig.  153  and 
the  practical  construction  is  shown  below  it. 
By  reference  to  the  figure  it  may  be  seen 
that  if  the  pipe  ab  contracts  so  that  b 
moves  to  J',  the  point  c  would  be  moved 
to  c\  where  hi/  =  C(f.  But  if  cd  =  ab,  dc 
would  also  contract  to  dc .  Therefore  if 
the  compensator  is  placed  midway  between 
the  cabin  and  the  signal,  the  cabin  end  of 
the  pipe  being  fixed,  a  point  at  the  signal 
end  would  retain  its  position  regardless  of  any  temperature  change. 
Practically  these  arcs  should  not  be  required  tc  work  through 
too  great  an  angle.  It  has  been  found  that  500  feet  is  a  desirable 
limit.  Therefore  if  a  signal  was  1,000  feet  away  fiom  the  cabin, 
two  compensators  should  be  used,  each  placed  250  feet  from  the 
ends.     Then  the  position  of  the  ends  and  the  middle  point  would 


192 


RAILROAD  ENGINEERING 


181 


be  unclianged  by  temperature.  It  should  be  noted  that  the  in- 
sertion  of  such  a  mechanism  changes  the  direction  of  the  motion 
of  the  pipe;  i.e.,  if  al  moves  to  the  right  cd  will  move  to  the 
left,  and  vice  versa.  Therefore  one  section  or  the  other  must  be  in 
compression,  and  such  a  com- 
pensator is  applicable  only  to 
pipes.  No  compensator  which 
is  equally  satisfactory  has  ever 
been  designed  for  use  with  wires. 
They  all  require  a  spring  or 
weight  which  takes  up  the  slack, 
but  if  the  wire  gets  caught  some- 
where this  spring  or  weight  may 
be  pulled  because  its  resistance 
is  less,  and  then  the  signal  does 
not  operate.  Several  designs  are 
in  use  and  they  work  satisfac- 
torily a«  long  as  the  mechanism 
is  in  order. 

148.  Electro=Pneumatic 
Signals,  The  mechanical  move- 
ment of  signals  by  wires  and 
rods  is  practically  limited  to 
about  2,000  feet  and  even  at  this 
distance  it  is  troublesome.  Elec- 
tric power  from  batteries  may  be 
used  when  the  power  required  is 
very  small.  An  electro-pneu- 
matic system  uses  compressed 
air  whose  power  can  be  sent  any- 
where through  pipes  and  which 
may  be  made  to  move  not  only 
signals  but  switches.  The  valves 
controlling  the  pistons  are  oper- 
ated electrically  by  a  current  of 
low  intensity,  which  may  be  provided  by  batteries  but  which  in  a 
plant  of  much  magnitude  is  more  economically  obtained  from 
storage  batteries  which  are  charged  from  a  dynamo.     The  operation 


Fig.  154.    Electro-Pneumatic  Signal 
Mechanism. 


193 


182 


RAILROAD  ENGINEERING 


of  the  valve  is  shown  in  Fig.  154.  In  the  position  shown  the 
magnet  is  not  energized.  When  it  is,  the  armature  (at  the  top) 
is  drawn  down,  which  opens  the  conical  valve  just  above  the  spring, 
and  the  air  passes  from  the  pressure  pipe  through  the  valve  and 
down  the  passage  alongside  of  the  valve  chamber  until  it  bears 

on  the  top  of  the  piston,  which 
is  shown  in  its  extreme  upward 
position.  When  the  piston  is 
forced  down,  it  will  raise  the 
counterweight  (see  Fig.  155)  and 
put  the  signal  at  "  clear."  When 
the  magnet  is  de-energized  for 
any  reason,  the  spring  forces  the 
valve  up,  the  air  in  the  cylinder 
escapes  through  the  exhaust  and 
the  counterweight  not  only  raises 
the  piston  to  the  top  but  draws 
the  signal  to  indicate  danger. 
A  failure  of  either  the  current 
or  the  pressure  will  thus  put  the 
signal  at  danger. 

149.  Electric  Semaphores. 
Still  another  modification  of  au- 
tomatic signals  is  the  electric 
semaphore,  which  is  a  semaphore 
of  the  usual  type,  operated  by 
an  electric  motor  of  about  \ 
horsepower,  themotor  obtaining 
its  current  from  a  set  of  10  to 
16  Edison-Lalande  battery  cells 
which  are  placed  in  a  box  at  the 
foot  of  the  signal  post.  The 
motor  winds  up  a  light  wire 
cable  which  raises  the  counterweight  and  thereby  sets  the  signal 
at  "  clear."  The  motor  is  started  and  stopped  by  the  action  of  a 
relay  connected  to  the  track  circuit.  The  track  circuit  has  the 
fundamental  principles  previously  described,  but  has  been  made 
somewhat  complicated  so  as  to  provide  for  the  operation  of  distant 


Fig.  155.    Electro-Pneumatic  Signal. 


194 


RAILROAD  ENGINEERING  183 

as  well  as  home  signals  and  also  the  protection  of  and  from  all 
switches  in  the  section.  For  the  details  of  the  track  circuits  the 
student  is  referred  to  the  more  complete  works  on  this  subject 
previously  mentioned. 

INTERLOCKING. 

150.  Principles.  The  interlocking  of  the  switches  and  sig- 
nals  of  a  large  terminal  yard  is  such  a  complicated  piece  of  mech- 
anism  that  any  adequate  explanation  and  description  would  require 
too  much  space  here.  Nothing  will  be  attempted  but  a  demon- 
stration of  the  fundamental  principle.  The  reason  for  the  necessity 
of  interlocking  is  simple.  A  mere  inspection  of  the  design  of  a 
complicated  yard  will  show  that  it  is  readily  possible  to  arrange  a 
» large  number  of  combinations  of  different  switch  movements  for 
the  operation  of  an  equal  number  of  trains  simultaneously.  But 
the  operation  of  such  switches  is  controlled  from  a  signal  cabin, 
and  unless  there  are  limitations  on  the  combinations  a  signalman 
would  be  liable  to  set  switches  and  signals  so  that  two  or  more 
trains  might  collide.  The  fundamental  principle  of  the  interlock- 
ing  device  is  comprised  in  the  following  statements: 

(a)  all  switch  signals  are  normally  at  danger; 

(h)  no  switch  lever  maybe  set  for  any  route  until  the  switches 
for  any  other  route  which  might  cause  a  collision  have  been  locked; 

(c)  the  signal  cannot  be  set  to  run  through  any  switch  until 
the  switch  itself  is  set. 

Although  an  engineman  may  cause  a  collision  by  running 
past  a  danger  signal,  the  worst  that  a  careless  signalman  can  do  is 
to  delay  traffic.  He  cannot  set  signals  and  switches  so  as  to  cause 
a  collision  or  even  a  "  side  swipe."  The  design  of  the  interlocking 
machine  must  therefore  be  based  on  a  study  of  the  safe  combina- 
tions, and  then  the  interlocking  machine  must  have  its  "  cross 
locks  "  and  "  locking  dogs  "  so  arranged  that  no  interference  is 
possible.  The  case  illustrated  in  Fig.  156  has  purposely  been 
made  as  simple  as  possible.  The  upper  part  shows  merely  the 
locking  dogs  (shaded  full  black)  which  are  fastened  on  to  the 
"  locking  bars "  (which  run  crosswise)  and  the  "  cross  locks " 
(shaded  with  cross  hatching),  which  move  at  right  angles  to  the 
locking  bars.     In  the  lower  part  of  the  figure  are  shown  the  signals 


195 


184 


RAILROAD  ENGINEERING 


and  tracks  for  a  crossover  from  a  main  track.  No.  1  is  the  dis- 
tant signal,  No.  2  is  the  home  signal  governing  the  main  track 
with  respect  to  the  crossover,  No.  8  are  the  switch  levers  which 
work  simultaneously,  No.  4  is  the  signal  governing  movement  from 
the  siding  to  the  main  track,  and  No.  5  is  the  signal  governing 
movement  from  the  main  track  to  the  siding.  No  lever  for  a  sig- 
nal or  a  switch  can  be  moved  without  simultaneously  moving  the 
locking  bar  (having  the  corresponding  number)  from  right  to  left 
as  shown  in  the  figure. 


4  ^'^'^''^s^  iocksV 


Jl  Locking    dogs. 


}< leoo' 


Fig.  156.    Interlocking. 

The  wedge-shaped  ends  of  the  locking  dogs  will  move  (if 
possible)  the  cross  locks  with  which  they  may  come  in  contact.  If 
any  cross  lock  is  immovable  because  it  is  already  in  contact  with 
some  other  locking  dog,  then  it  will  be  impossible  to  move  that 
lever  until  the  lever  (or  levers)  controlling  all  interfering  locking 
dogs  have  been  so  moved  as  to  remove  the  obstruction.  The  posi- 
tion of  the  locking  dogs  in  Fig.  156  is  that  for  all  signals  normal 
or  at  "danger."  Suppose  it  were  attempted  to  ''clear"  signal 
No.  1.  To  do  so,  locking  bar  No.  1  must  move  the  cross  lock 
No.  1.  But  this  is  impossible  since  one  of  the  dogs  on  locking 
bar  No.  2  interferes.     Lever  No.  1  cannot  therefore  be  moved  until 


196 


RAILROAD  ENGINEERING  185 

lever  No.  2  has  been  cleared,  which  operation  will  move  that  dog  far 
enough  to  the  left  so  that  the  cross  lock  can  move  up.  And  this 
is  in  accordance  with  the  principle  previously  stated  that  a  distant 
signal  should  not  be  cleared  until  its  home  signal  is  cleared. 

As  another  illustration,  when  the  signal  No.  2  has  been 
cleared,  the  locking  bar  No.  2,  by  means  of  its  attached  dogs, 
moves  the  cross  lock  No.  2  upward.  This  cross  lock  is  then  set 
against  locking  dop;s  on  each  of  locking  Vmrs  No.  3  and  No.  5  and 
prevents  them  from  being  cleared.  Of  course  the  signals  for  the 
crossover  should  not  be  cleared  while  the  signal  is  set  for  a  clear 
main  track. 

Exercise.  The  student  should  draw  a  modification  of  the 
upper  part  of  Fig.  156,  as  it  would  be  placed  to  indicate  that  the 
switch  was  set  for  a  crossing  from  the  siding  to  the  main  track. 
It  should  be  noted  that  signal  No.  4  is  set  "clear"  when  it  is  de- 
signed to  move  along  the  siding  without  using  the  switch,  and 
No.  5  is  set  clear  when  the  switch  is  set  so  that  a  train  could  run 
backward  past  the  switch  without  using  it.  Both  No.  4  and  No. 
5  are  set  at  "danger"  when  it  is  designed  to  run  from  one  track  to 
the  other. 

The  cross  locks  No.  1  to  No.  4  inclusive  are  each  in  one  piece 
with  notches  cut  for  the  dogs.  Cross  lock  No.  5  has  the  upper 
part  separate.  When  the  lower  part  is  moved  it  does  not  move 
the  upper  part  unless  the  "tappet"  on  locking  bar  No.  3  has  previ- 
ously been  moved  between  the  parts.  The  tappet  is  unnecessary 
with  the  simple  combination  of  levers  shown,  but  might  be  neces- 
sary with  a  somewhat  more  complicated  system. 

Of  course  the  above  description  makes  no  mention  of  a  multi- 
tude of  details  necessary  for  a  manual  machine,  to  say  nothing  of 
the  complication  required  tor  an  electro- pneumatic  interlocking 
machine.  But  w^hatever  the  complication  or  how  many  may  be 
the  number  of  levers,  the  interlocking  principle  is  as  above. 

TRACK   MAINTENANCE. 

151.  Tools.  Tools  should  be  of  good  quality  and  well 
designed  for  their  use.  Economy  in  this  respect,  to  save  initial 
cost,  is  apt  to  increase  the  labor  item  and  since  the  labor  costs  over 
60  per  cent  of  the  total  cost  of  track  maintenance,  a  very  little 


197 


186  RAILROAD  ENGINEERING 

discouragement  of  labor  owing  to  inefficient  tools  would  more  than 
overbalance  any  possible  saving  in  cost.  The  list  of  tools  required 
for  the  varied  work  of  a  track  gang  is  quite  large,  and  therefore  an 
effort  should  be  made  to  pare  down  the  list  as  much  as  is  practicable 
or  safe,  because  it  is  correspondingly  difficult  for  a  track  foreman 
to  prevent  losses  due  to  carelessness.  The  following  list  is  based 
on  the  requirements  of  a  gang  of  six  trackmen  and  a  foreman. 

A  large  proportion  of  the  tools  are  for  work  on  which  not 
more  than  one  or  two  men  need  work  at  any  one  time.  When  the 
list  calls  for  six  or  more  of  any  one  tool,  they  are  always  the  tools 
which  are  in  constant  or  excessive  use,  or  which  are  liable  to 
become  quickly  broken,  and  of  which  an  extra  supply  is  a  neces- 
sity for  use  while  waiting  for  requisitions  to  make  up  for  loss  or 
breakage.  The  list  is  taken,  with  some  slight  modifications,  from 
Camp's  Notes  on  Track. 

Adzes 2   Grindstone 1  Scythes — grass 4 

Ax— chopping 1   Hanamers— spike 4  "      —brush 4 

Ax — hand 1  "    — sledge — 16  lbs .  1  Snaths 4 

Auger,  2-inch 1  "    — strike — 10  lbs.  1  Shovels — track 8 

Bars — claw 2  •'    — nail — claw  ...  1          '*      — scoop 4 

'*    —crow 0       "    —ballast* 6         "      —long  handle  1 

"    —pinch 6   Hatchet 1  Saw— hack,  blades ...  12 

"    — raising 1   Hoe— garden 1       "  "      frame  ...   1 

"   — tamping 8  Jack — track 1      "       hand 1 

Brace  and  bits 1    Key — switch 1      "       crosscut 1 

Brooms  (coarse) 2   Lanterns — white 2  Screwdriver 1 

Brush  hooks 2  "       —red 2  Spade 1 

Car— hand 1  "       -green 2  Steel  square 1 

" — push 1   Level  board 1  Tape   (50',  graduated 

Car  chains 2  "    — spirit — pocket  1       to  tenths) 1 

Chisels — cold 2  Locks — switch — extra  2  Tongs — rail 4 

"      —track 12   Mattocks 2  Tool  box 1 

"      —wood 1   Oil  can— 1  gal 1  Tool  checks 6 

Curving  hooks 2     "     *'  — 2  "  1  Torpedoes  (with  box). 24 

Chalk  line 100  ft.   Oiler— squirt 1  Verona  spike  puller . .   1 

Ditch  line 150  ft.    Padlocks 2  Vise 1 

Drawshave 1    Picks 8  Water  pail  or  jug 1 

Dippers  (or  cups) ... .  2        "    — tamping* 8  Weed  scuffles 6 

Files 3   Punch — hand 1  Wheelbarrows 3 

Flags— red 4   Rake— garden 1  Whetstones 4 

<<    — green 2   Rail  drill 1  Wire  stretcher 1 

Forks— ballast* 4       "       *'     bits 6  Wrenches— track 3 

Gauge 1   Rule — two-foot 1         "      — monkey  (8")  1 

*  Needed  only  in  stone  baUast. 

198 


RAILROAD  ENCxINEERINO  1S7 

The  first  comment  on  the  above  list  is  in  regard  to  the  bars 
of  various  kinds.  Claw  hars  are  used  for  spike  pulling.  The 
ideal  design  is  one  that  would  permit  pulling  the  spike  with  one 
stroke  without  changing  the  fulcrum,  and  that  will  also  pull  it 
clear  out  without  bending.  Apparently  this  is  mechanically  im- 
possible and  in  spite  of  the  many  efforts  which  have  been  made  and 
the  new  designs  which  have  been  brought  out,  the  old  "bull's 
foot "  claw  bar  seems  to  be  the  best. 

The  "  Verona  spike  puller''^  is  attached  to  a  spike  which  is 
in  a  confined  place  (such  as  behind  a  guard  rail)  and  is  operated 
by  means  of  an  ordinary  claw  bar  resting  on  top  of  the  rail. 

"  Crovj "  ha7's  are  considered  to  be  those  which  taper  down 
symmetrically  to  a  wedge-shaped  edge  at  the  so-called  "point," 
in  contradistinction  to  " pinch  ^^  hars  on  which  the  chisel  edge  is 
even  with  (or  outside  of)  the  face  line  of  the  bar.  The  number 
of  crow  bars  is  put  at  "  0  "  to  emphasize  Mr.  Camp's  opinion  that 
the  crow  bar  form  should  not  be  used  and  that  the  pinch  bar  form 
is  far  preferable. 

Tamping  hars  should  not  weigh  more  than  10  pounds  nor 
should  they  be  more  than  5  ft.  3  in.  long.  If  the  handle  is  solid  it 
is  rather  small  and  hard  to  hold.  It  is  therefore  sometimes  made 
as  a  pipe,  with  a  malleable  tamper.  Another  form  uses  a  wooden 
handle. 

Track  chisels  are  cold  chisels  provided  with  a  handle  of  wood 
by  which  they  may  be  more  readily  and  safely  held  in  position. 
They  should  be  about  1^  in.  square  and  8  in.  long,  made  of  tool 
steel.  A  single  blow  may  break  them  or  render  them  useless 
until  re-tempered  and  re-ground,  and  therefore  a  large  number  is 
necessary. 

Gauges.  These  may  be  divided  into  three  classes.  The  first 
is  the  "  home-made  "  type  of  wooden  gauge  which  is  perhaps  brass 
bound.  One  common  objection  to  this  form  consists  in  the  danger 
that  it  will  not  always  be  placed  truly  at  right  angles  to  the  track. 
The  effect  of  this  error  is  to  make  tight  gauge.  To  obviate  this 
error,  the  "Huntington  "  track  gauge  has  at  one  end  two  lugs 
about  seven  inches  apart  and  one  lug  at  the  other  end.  The  gauge 
is  the  distance  from  the  single  lug  to  the  middle  point  of  the  seven - 
inch  line,  the  two  lines  being  at  right  angles.     The  device  is  theo- 


199 


188  RAILROAD  ENGINEERING 

retically  perfect  provided  that  the  two  lugs  at  the  one  end  are  both 
in  contact  with  the  head  of  the  rail.  A  slight  error  in  this  respect 
will  make  the  gauge  too  wide.  The  "  Warren  "  gauge  has  two 
short  circular  arcs  forming  part  of  a  complete  circle,  whose  diam- 
eter is  the  gauge,  fastened  to  the  gauge  bar. 

Hammers.  For  section  work,  spike  hammers  should  not 
w^eigh  more  than  8  pounds  and  have  a  length  of  about  10|  inches. 
Th^  16-pound  sledge  is  only  needed  for  occasional  very  heavy 
work,  when  it  is  however  almost  essential.  The  10-pound  striking 
hammer  is  the  better  one  to  use  with  track  chisels  rather  than  to 
use  the  spiking  hammers  as  is  so  frequently  done.  The  ballast 
hammers  are  only  used  for  breaking  up  stone  for  ballast  and  are 
unnecessary  even  for  this  purpose  if  machine  broken  ballast  of 
uniform  size  is  furnished. 

Truck  jack.  One  of  these  is  illustrated  in  Fig.  107.  They 
are  certainly  handy  and  economical  tools  for  the  track  gang,  but 
more  than  one  serious  wreck  has  been  caused  by  the  inability  of 
the  gang  to  remove  the  jack  before  the  arrival  of  an  unexpected 
train,  and  as  a  derailing  device  a  jack  is  exceptionally  effective. 
Track  instructions  generally  specify  that  they  must  not  be  placed 
between  the  rails. 

Level  hoard.  Such  a  board  usually  has  a  level  tube  sunk  in 
the  upper  edge.  At  one  end  a  series  of  steps  are  cut,  each  with 
a  base  of  about  two  inches,  and  with  risers  of  one-half  inch,  begin- 
ning at  the  lower  edge.  The  discussion  on  the  superelevation  of 
the  outer  rail  (see  §  119)  shows  the  foolishness  of  over- refinement 
in  such  work.  If  the  required  superelevation  is  2.5  in.,  the  fifth 
step  of  the  board  may  be  placed  on  the  outer  rail  and  the  plain 
end  on  the  inner  rail.  When  the  track  is  properly  adjusted  the 
bubble  should  be  in  the  center.  Of  course  the  adjustment  of  the 
level  bubbles  should  be  carefully  watched  and  frequently  adjusted 
if  necessary. 

Shovels.  The  best  shovel  for  track  work  is  the  short  handled 
shovel  with  square  point,  made  out  of  a  single  piece  of  crucible 
steel.  The  blade  should  have  a  length  of  about  12  in.  When 
this  has  been  worn  dow^n  to  9  in.  it  should  be  thrown  away— for 
track  work.     Its  use  is  then  uneconomical.     The  scoop  shovels  are 

200 


RAILROAD  ENGINEERING  189 

for  handling  cinders  and  packed  snow.     The  long-handled  shovel 
is  for  digging  post  holes.     It  should  be  round-pointed. 

The  above  list  includes  only  the  tools  which  will  be  required 
by  almost  any  track  gang.  Cant-hooks  and  peavies  are  frequently 
necessary  for  handling  timber.  Blasting  drills,  wedges,  powder 
and  fuse  are  sometimes  needed  to  break  up  masses  of  rock  which 
may  have  fallen  into  a  cut.  Culverts  and  bridge  channels  get 
choked  up  with  timber  and  debris  of  various  kinds  which  may  need 
ropes  and  tackle  to  clear  them.  A  jim-crow  rail  bender  is  occa- 
sionally necessary,  although  one  such  may  be  made  to  sei^ve  two  or 
more  section  gangs. 

152.  Work  Trains.  The  work  of  a  track  gang  is  usually 
confined  to  one  "  section,"  which  is  usually  not  more  than  five 
miles  long,  and  which  on  roads  of  the  very  heaviest  traffic  may  be 
shortened  up  to  a  mile.  On  exceptionally  poor  light  tragic  roads, 
they  are  made  eight  and  even  ten  miles.  For  ordinary  work  their 
hand  car  and  push  car  furnish  all  needed  transportation  facilities 
for  themselves  and  materials.  But  there  is  much  work  which  is 
more  irregular  in  its  character,  which  must  be  handled  on  a  larger 
scale,  and  which  requires  for  economy  a  work  train.  Such  work  is 
the  distribution  of  track  materials  such  as  ties,  rails  and  ballast 
from  the  sources  of  supply  to  the  places  on  the  road  where  they  are 
needed.  Also,  when  re-ballasting  is  to  be  done  on  an  extensive 
scale,  when  heavier  rails  are  to  be  substituted  throughout,  or,  in 
short,  when  there  is  any  work  to  be  done  which  is  beyond  the 
routine  work  of  keeping  the  track  up  to  its  normal  condition,  then 
a  work  train  with  its  usual  force  of  laborers  can  accomplish  the 
work  with  greater  economy. 

The  work  train  is  usually  hauled  by  the  worst  engine  on  the 
road,  sometimes  by  one  which  would  otherwise  be  sent  to  the  scrap 
heap.  Whatever  the  justification  of  this  policy,  it  may  be  carried 
so  far  that  the  regular  train  service  suffers  by  the  inability  of  the 
work  train  to  keep  out  of  the  way  of  regular  traffic,  or  else  there  is 
the  false  economy  of  wasting  the  time  of  the  work  train  gang  while 
trying  to  save  by  utilizing  a  worthless  engine.  A  passenger  engine 
which  may  have  proved  too  light  for  regular  service  is  preferable 
to  a  freight  engine,  since  the  work  train  should  be  capable  of  mak- 
ing good  speed  in  running  to  a  siding  and  the  load  is  usually  lit/ht. 

201 


190  RAILROAD  ENGINEERING 

^he  minimum  requirements  for  the  train  should  include  a  large 
caboose  and  a  flat  car  provided  with  large  tool  boxes  for  picks, 
shovels,  bars,  hammers  and  other  track  tools.  Underneath  the 
caboose  may  be  hung  a  large  box  in  which  may  be  stored  ropes, 
*»pulley  blocks,  chains,  jacks,  etc.  Since  the  cost  of  train  crew 
wages,  fuel,  and  other  expenses  which  must  be  charged  up  for  the. 
use  of  the  rolling  stock  will  aggregate  about  $25  per  day,  there 
should  be  enough  laborers  attached  to  the  train,  and  their  work 
should  be  so  planned  as  to  justify  this  additional  expenditure. 

The  minimum  number  of  laborers  should  be  about  20,  and 
this  should  be  increased  to  as  many  as  can  be  profitably  employed. 
Since^  the  work  of  the  train  is  scattered  over  a  great  distance,  the 
company  must  choose  between  wasting  considerable  time  both 
morning  and  evening  while  carrying  the  gang  to  and  from  their 
homes,  together  with  many  miles  of  train  service,  or  of  providing 
boarding  cars,  provided  with  bunks  and  one  or  two  cars  for  kitchen 
and  dining  cars.  One  large,  clean  box  car  can  be  easily  and 
cheaply  fitted  up  as  kitchen  and  dining  car  for  24  men.  If  the 
crew  is  much  larger,  one  car  should  be  devoted  to  kitchen  and  the 
storage  of  supplies  and  another  car  used  for  a  dining  car.  An 
ordinary  box  car,  or  an  old  passenger  car  can  be  readily  fitted  up 
with  four  double  lower  berths  and  four  double  upper  berths  on  one 
side  and  four  lower  and  four  upper  single  berths  on  the  other  side, 
thus  accommodating  24  men.  Even  better  accommodations  may 
be  provided  when  the  need  for  such  a  train  and  gang  is  so  regular 
that  it  will  have  practically  permanent  employment.  A  little 
extra  money  spent  by  the  company  in  providing  comforts  for  the 
men  is  immediately  repaid  in  a  better  quality  of  work  and  less 
straggling  off. 

153.  Ditching.  While  the  routine  clearing  up  of  ditches  is 
part  of  the  work  of  a  section  gang,  it  will  frequently  happen, 
especially  when  the  slopes  have  a  disintegrating  soil,  and  also  when 
the  slopes  have  been  made  originally  too  steep,  that  the  winter's 
frosts  will  fill  up  the  ditches  to  such  an  extent  that  it  is  best  taken 
out  with  a  work  train  gang.  Ordinarily  the  section  gang  would 
need  to  load  such  material  on  their  push  car  or  on  wheelbarrows 
and  run  the  material  out  to  the  end  of  the  cut  where  it  may  be 
harmlessly  wasted.     If  the  cut  is  very  long,  such  hauling  would 

202 


RAILROAD  ENGINEERINCx  191 

be  very  expensive.  Since  the  regular  schedule  will  not  usually 
j)ermit  the  train  to  stand  long  on  the  main  track,  especially  on  a 
single-track:  road,  the  loading  must  be  done  in  the  shortest  possible 
time.  This  usually  implies  that  a  part  of  the  gang  should  remain 
at  the  cut  while  the  train  is  running  off  to  unload  and  that  they 
should  all  work  there  if  the  train  must  run  to  a  siding  merely  to 
let  a  regular  train  pass.  During  such  times  the  men  can  scrape 
down  all  loose  material  from  the  side  slopes  and  loosen  up  the  fill- 
ing in  the  ditch,  so  that  it  is  all  ready  for  shovelling  when  the 
train  arrives. 

When  the  cuts  are  not  very  deep,  such  material  is  sometimes 
thrown  up  on  the  top  of  the  bank,  even  by  using  a  temporary 
staging  on  which  the  earth  is  thrown  and  then  again  shoveled  to 
the  top  of  the  bank.  In  any  such  case  the  earth  should  be  thrown 
well  back  from  the  edge  of  the  bank  so  as  to  guard  against  its 
being  again  w^ashed  into  the  cut.  It  also  should  not  interfere  with 
the  surface  ditch  which  should  have  been  cut  on  the  top  of  the 
bank  to  prevent  surface  water  from  the  slope  above  from  running 
down  into  the  cut. 

154.  Distributing  Ties.  The  methods  to  be  used  necessarily 
vary  with  the  sources  of  supply.  If  ties  were  obtainable  from 
farmers  and  were  delivered  along  the  right-of-way  on  every  sec- 
tion of  the  road,  very  little  if  any  distribution  by  a  work  train 
would  be  necessary.  When,  as  the  other  extreme,  there  is  no  local 
source  of  supply,  the  ties  must  be  hauled  many  miles  and  so  dis- 
tributed that  subsequent  distribution  by  the  trackmen  will  be 
reduced  to  a  minimum.  Since  economy  requires  that  ties  shall 
only  be  replaced  by  an  actual  count  of  those  which  are  defective, 
an  essential  preliminary  is  that  a  marker  shall  be  placed  along  the 
the  track  for  every  ten  ties  required,  or  that  the  number  required 
between  two  consecutive  telegraph  poles  shall  be  marked  on  the 
poles  so  that  it  may  be  seen  as  the  train  approaches.  By  this 
means  ties  may  be  thrown  off  as  required  while  the  train  is  mov- 
ing at  a  speed  of  about  six  miles  per  hour.  On  light  traffic  roads 
the  work  of  tie  distribution  is  frequently  done  by  the  local  freight 
train.  While  this  may  be  and  often  is  the  best  policy,  the  cost 
per  tie  is  much  greater. 


20.S 


192  RAILROAD  ENGINEERING 

155.  Distributing  Rails.  The  method  of  liandling  rails  de- 
pends very  largely  on  the  cars  on  which  they  are  loaded,  and  also 
on  their  length.  They  are  dropped  off  most  easily  when  loaded  on 
to  flat  cars,  but  frequently  they  are  loaded  on  to  gondolas  and  even 
in  box  cars  by  making  a  hole  in  the  end  of  the  car.  Rails  of  45 
and  60  feet  can  only  be  loaded  on  to  two  consecutive  flat  cars.  If 
they  are  being  unloaded  in  one  place  simply  for  storage,  a  derrick 
of  some  kind,  even  though  temporary,  is  wise  economy.  For  dis- 
tribution along  the  track  they  are  either  dropped  over  the  side  of 
the  car  or  pulled  off  from  the  end.  If  they  are  dropped  over  the 
side  they  are  apt  to  be  kinked.  Sometimes  they  are  slid  off  on  skids 
made  of  two  timbers  or  pieces  of  rail  about  10  feet  long,  but  this 
is  impracticable  in  some  localities  and  it  lands  the  rail  at  some  dis- 
tance from  the  track.  The  car  to  be  immediately  unloaded  may 
be  placed  at  the  extreme  rear  of  the  train.  Then  a  rail  hook  at- 
tached to  a  sufficient  length  of  rope  may  be  hooked  into  one  of  the 
bolt  holes  and  the  rail  may  be  drawn  off  the  end.  By  placing  a 
"dolly"  on  the  end  of  the  car  the  rail  may  readily  be  drawn  off  by 
hand.  As  soon  as  the  center  of  gravity  passes  the  dolly,  the  outer 
end  falls  easily  to  the  track  and  then,  pulling  the  train  ahead,  the 
other  end  is  let  down  easily  as  it  drops  off.  Sixty- foot  rails  are  so 
flexible  that  a  considerable  part  of  the  length  will  be  resting  on 
the  ground  before  the  other  end  leaves  the  car,  and  will  not  be  in- 
jured by  dropping  on  the  ties. 

When  the  rails  are  especially  long  and  heavy,  an  easier  method 
is  to  hook  on  the  rail-hook  and  attach  the  ropes  to  a  track  rail  or 
around  a  tie.  Then  let  the  train  move  ahead  until  the  rail  is 
drawn  off.  Even  the  dolly  under  the  rail  at  the  end  of  the  car  is 
unnecessary  with  this  method.  If  rails  are  needed  for  both  sides, 
two  such  ropes  and  hooks  may  be  used  simultaneously.  With  a 
little  more  care  this  may  be  so  done  that  the  end  of  each  rail  comes 
almost  exactly  at  the  required  joint,  even  allowing  for  staggering 
the  joints  on  the  two  lines  of  rails.  By  attaching  a  push  car  to 
the  car  carrying  the  rails,  the  rails  may  pass  over  that  and  down 
on  to  the  ground  without  any  danger  of  injury  from  the  drop. 

The  reverse  operation— loading  old  rails  onto  a  car — is  heavy 
and  costly  work  when  done  by  hand.  The  best  plan  is  to  do  it  by 
means  of  a  derrick.     If  it  must  be  done  without  such  aid,  it  facili- 


204 


RAILROAD  rxniXI-ERIXO  193 

tates  the  work  to  make  an  inclined  plane  by  attacliincr  a  push  car 
to  the  Hat  car  on  wliich  the  rails  are  to  l)e  loaded,  and  then  by 
placing  several  dollies  on  this  plane,  the  rails  may  run  up  on  rollers 
with  a  minimum  of  actual  lifting.  ItMiiight  be  thought  that  a 
70-lb,  rail,  30  feet  long,  which  weighs  700  pounds,  should  not  be 
an  excessive  load  for  six  men.  AVhen  the  men  are  carefully  drilled 
to  lift  together  and  simultaneously  raise  the  rail  above  their  heads 
and  throw  it  with  machine-like  precision  on  to  the  car,  it  may  be 
(and  is)  successfully  done  in  this  way,  but  if  one  or  two  men  shirk 
or  do  not  lift  with  the  others,  the  load  is  concentrated  on  the  others. 
They  successively  become  frightened  and,  to  save  themselves,  "jump 
from  under";  the  remainder  cannot  sustain  the  load  and  it  falls. 
It  is  lucky  if  someone  does  not  have  a  foot  crushed.  The  longer 
and  heavier  rails  cannot  be  handled  in  this  way. 

156.  Handling  Ballast.  A  railroad  must  consider  itself 
unfortunate  if  it  does  not  have  a  gravel  bank  at  some  place  along 
its  line.  The  bank  generally  extends  into  the  adjoining  property, 
which  is  either  bought  outright  or  the  gravel  privilege  is  bought. 
The  last  method  generally  specifies  that  the  top  soil  shall  be  reserved 
and  spread  upon  the  excavation  after  the  gravel  is  exhausted.  The 
gravel  is  usually  overlaid  with  more  or  less  vegetable  soil.  Some- 
times the  amount  of  this  is  so  insignificant  that  its  presence  may 
be  ignored,  but  if  the  depth  is  appreciable  it  will  pay  to  strip  it. 
A  spur  track  whose  minimum  length  is  the  length  of  the  train 
must  be  run  off  from  the  main  track.  The  method  of  attacking 
the  bank  depends  on  the  method  of  digging — whether  by  steam 
shovel  or  by  hand  digging  and  shoveling. 

About  twenty  cubic  yards  per  day  may  be  considered  a  fair 
day's  work  in  loading  gravel  cars  at  the  pit.  A  steam  shovel  with 
a  dipper  holding  IJ  to  2  cubic  yards  can  load  800  to  1,200  cubic 
yards  per  day,  depending  on  the  prompt  handling  of  the  cars  when 
loaded.  Even  this  figure  has  been  greatly  increased  under  excep- 
tionally favorable  conditions.  But  the  use  of  a  steam  shovel  implies 
the  use  of  a  locomotive,  which  must  be  constantly  at  the  pit  shift- 
ing the  cars  so  that  there  is  a  car  constantly  in  place  within  range 
of  the  shovel.  The  cost  of  running  such  a  shovel  with  its  attendant 
locomotive  will  be  about  $50  per  day.  This  will  pay  about  40 
laborers  who  could  dig  about  800  cubic  yards.     Therefore,  unless 

205 


194  RAILROAD  ENGINEERING 

the  circumstances  are  so  favorable  that  the  shovel  can  exceed  800 
cubic  yards  per  day,  the  work  may  be  done  about  as  cheaply  by 
hand  shoveling.  This  is,  however,  about  the  limiting  case.  With 
good  management  a  large  shovel  can  take  out  gravel  much  cheaper 
than  it  can  be  done  by  hand.  20  cubic  yards  per  day  at  a  labor 
cost  of  $1.25  per  day  makes  the  gravel  cost  about  six  cents  per 
cubic  yard  loaded  on  the  car  at  the  pit.  The  average  cost  of  such 
hauling  on  a  Western  railroad  was  computed  by  the  management 
to  be  0.35  cent  per  cubic  yard  per  mile.  In  this  case  the  quantity 
handled  was  very  large  and  the  cost  may  be  considered  exception- 
ally low. 

When  the  work  is  done  on  a  small  scale,  and  especially  when 
the  gravel  is  loaded  by  hand,  hand  methods  would  be  used  for 
unloading,  but  there  is  great  economy  in  the  use  of  a  plow  for 
unloading.  This  implies  the  use  of  flat  cars,  which  are  in  fact 
almost  universally  used  for  ballast  work — barring  the  special  pat- 
ented ballast  cars.  The  plows  are  "center  unloading"  or  "side 
unloading,"  and  some  of  the  most  recent  forms  are  adjustable  so 
that  they  will  unload  all  to  either  side  or  will  unload  to  both  sides 
in  any  desired  proportion.  The  plow  is  drawn  over  the  tops  of  the 
cars  by  a  cable.  The  cheapest  method  is  to  stop  the  train  where 
desired,  set  the  brakes,  uncouple  the  locomotive  and  attach  to  it  a 
1^"  or  1^"  wire  cable.  Commencing  with  the  plow  at  the  rear  car 
the  locomotive  moves  ahead  and  draws  the  plow  over  all  the  cars. 
This  method  has  many  objections,  especially  when  it  is  done  on 
curves.  A  much  better  method  is  to  have  a  car  carrying  a  hoisting 
engine,  which  may  be  supplied  by  steam  from  the  locomotive  by  a 
flexible  tube,  if  the  car  carrying  it  is  placed  immediately  behind 
the  locomotive,  or  preferably  which  is  supplied  from  its  own  boiler 
placed  on  the  car.  A  wire  rope  from  this  engine  hauls  the  plow. 
One  great  advantage  of  this  method  lies  in  the  fact  that  the  train 
can  be  kept  moving  if  desired  while  the  plow  is  working. 

If  it  is  desired  to  distribute  less  ballast  per  car  length  than 
the  car  load,  it  may  be  done  by  moving  the  train  ahead  at  just 
such  a  speed  that  will  give  the  desired  result.  Incidentally,  this 
method  is  very  useful  when  making  a  fill  from  a  trestle  or  to  fill  up 
a  washout.  By  putting  the  plow  at  the  rear  of  the  train  and  drawing 
the  plow  backward,  the   speed  of  the  train  and  of  the  plow  can 

206 


RAILROAD  ENGINEERING  195 

be  so  regulated  that  the  material  will  be  deposited  with  as  great 
concentration  as  desired.  If  it  is  desired  to  fill  up  a  hole,  the 
whole  train  load  may  be  deposited  in  one  spot  by  simply  hauling 
the  plow  back  as  fast  as  the  train  moves  forw^ard.  The  average 
cost  of  thus  unloading  with  a  cable  has  been  computed  as  about 
one-half  cent  per  cubic  yard.  During  recent  years  many  styles  of 
ballast  cars  which  are  easily  and  automatically  unloaded  have  been 
placed  on  the  market.  Some  of  these  have  been  designed  with  the 
distinct  idea  of  being  used  in  connection  with  local  freight  trains. 
They  are  picked  up  at  the  gravel  pit  by  a  local  freight  going  in 
the  desired  direction,  are  hauled  to  places  along  the  road  which 
have  been  previously  marked  with  stakes,  are  dumped  with  a  delay 
of  only  a  minute  or  so,  then  hauled  on  to  where  they  may  be  side- 
tracked and  hauled  back  to  the  pit  by  another  local  freight.  Gon- 
dola and  coal  cars  having  hopper  bottoms  are  also  used  extensively 
for  hauling  ballast. 

157.  Trestle  Filling.  This  "has  become  a  very  common  form 
of  work  for  the  work  train.  When  the  construction  of  a  railroad 
is  once  definitely  decided  and  work  is  begun,  any  measure  which 
will  hasten  the  opening  of  the  road  for  traffic  hag  a  very  high 
money  value.  Therefore  trestles  have  been  built  where  embank- 
ments are  a  better  form  of  permanent  construction.  The  prelimi- 
nary construction  of  trestles  is  further  justified  by  the  fact  that 
the  immediate  construction  of  an  embankment  would  often  involve 
very 'expensive  hauling  with  teams  from  borrow  pits  in  the  neigh- 
borhood, while  a  future  fill  may  be  made  by  the  train  load,  as  des- 
cribed below,  at  a  much  less  cost.  Incidentally,  time  is  allowed  to 
determine  the  maximum  water  flow  through  the  hollow  crossed  by 
the  line,  and  the  size  of  the  culvert  required  may  be  more  accu- 
rately determined.  The  cost  of  the  culvert,  which  may  be  very 
considerable,  is  also  deferred  to  a  time  when  the  road  can  better 
afford  it.  At  the  time  that  many  existing  trestles  were  built  the 
cost  of  timber  in  their  localities  was  so  small  that  the  trestle  may 
have  been  actually  cheaper. 

Many  roads  are  now  confronted  by  the  necessity  of  either 
replacing  the  trestle  or  filling  in  with  earth.  While  the  relative 
cost  is  very  variable,  depending  on  the  local  price  of  timber,  the 
proximity  of  a  sufficient  supply  of  available  filling  and  the  methods 

207 


190  RAILROAD  ENGINEERING 

to  be  employed,  yet  as  an  approximate  figure  it  may  be  said  that 
iills  as  high  as  25  feet  may  be  filled  with  earth  as  cheaply  as  a 
trestle  can  be  reconstructed.  But  when  it  is  considered  in  addi- 
tion that  the  average  amount  of  timber  required  annually  for 
repairs  of  trestles  is  about  one-eighth  of  the  volume,  also  that  the 
labor  involved  in  maintenance  is  very  great  while  it  is  almost  in- 
significant on  an  embankment,  also  that  the  danger  of  accident  on 
a  trestle  and  the  disastrous  results  of  a  derailment  which  may  occur 
on  a  trestle  is  so  much  greater  than  on  an  embankment,  the  height 
at  which  it  becomes  economical  to  fill  with  earth  instead  of  recon» 
structing  the  trestle  increases  until  it  may  reach  50  feet.  But  the 
filling  in  of  high  trestles  involves  several  special  constructive 
features.  The  hollow  may  have  at  the  bottom  a  very  soft  soil 
which  cannot  sustain  a  heavy  embankment  without  considerable 
settlement.  Such  a  settlement  will  prove  destructive  to  almost 
any  culvert  unless  a  solid  foundation  may  be  made  for  it.  Under 
such  conditions  a  pile  or  concrete  foundation  for  the  culvert  may 
become  a  necessity. 

The  dumping  of  earth  and  particularly  of  boulders,  stumps 
and  clods  of  frozen  earth  may  do  serious  injury  to  the  trestle  unless 
means  are  taken  to  guard  against  it.  This  may  be  done  by  placing 
an  "apron"  on  each  side  which  will  deflect  the  earth  so  that  it  falls 
outside  the  trestle.  As  the  piles  grow  on  each  side  the  intermediate 
space  will  be  filled  up.  The  longitudinal  braces  which  are  most 
apt  to  suffer  are  sometimes  strengthened  by  heavy  timbers,  which 
may  be  old  stringers,  etc.  The  filling  should  be  done  regularly 
along  the  length  so  that  the  bents  will  not  be  forced  out  of  place 
by  an  unsupported  pressure  of  earth  on  one  side.  If  the  bank  is 
formed  merely  by  dropping  earth  loosely  from  above,  its  slopes 
will  be  steeper  than  can  be  retained  permanently.  The  result  is 
frequently  a  disastrous  slip.  This  feature  justifies  the  spreading 
of  the  earth  by  scrapers  as  the  filling  proceeds.  This  method  has 
the  additional  merit  of  packing  the  earth  so  that  there  is  almost  no 
settlement  and  the  stringers  may  be  pulled  and  the  ballasted  road- 
bed may  be  constructed  very  soon  after  the  filling  is  complete. 
Otherwise  the  settlement  is  so  great  that  six  months  or  a  year 
must  elapse  before  track  laying  is  permissible.     During  this  time 

208 


RAILROAD  ENGINEERING  197 

the  embaiikiiient  may  settle  10  per  cent.  This  earth-spreading 
may  be  done  for  two  or  three  cents  per  cubic  yard. 

The  choice  of  filling  material  is  an  important  matter.  A 
sandy  or  gravelly  soil  is  the  best.  Clay  is  apt  to  be  very  trouble- 
some, for,  no  matter  how  hard  it  may  be  in  dry  weather,  it  will 
slip  and  run  when  it  becomes  w^et.  This  is  especially  true  w^hen 
the  base  of  a  fill  is  on  a  steep  side  slope.  In  this  case  the  whole 
fill  may  slide  down  the  hill.  One  means  of  preventing  this  is  to 
dig  trenches  along  the  slope.  Even  plowing  the  surface  in  contour 
furrows  may  be  sufficient  to  prevent  such  a  slip.  The  material  for 
such  a  fill  will  usually  come  as  the  spoil  from  a  widened  cut,  loaded 
perhaps  w^ith  a  steam  shovel  into  dump  cars  or  on  to  flats  from 
which  it  is  scraped  by  a  plow,  as  previously  described. 

The  practice  of  immediately  planting  tufts  of  Bermuda  grass 
and  even  tree  slips  which  w^U  take  root  and  grow  and  thus  bind 
the  embankment  together  as  well  as  cover  it  wnth  a  surface  of  sod 
which  will  protect  it  from  rain-wash  is  a  measure  of  true  economy 
which  always  pays.  The  total  cost  of  such  a  fill  must  combine  the 
cost  of  loading,  hauling,  spreading  (if  it  is  done)  and  the  other 
expenses  incidental  to  making  a  finished  embankment,  but  the 
record  made  by  many  roads  on  these  items  show  that  it  may  be 
done  at  very  much  less  cost  than  by  the  methods  which  are  usual 
or  possible  during  the  original  construction  of  the  road. 

158.  Organization  of  Track  Maintenance  Labor.  Although 
there  is  much  variation  in  the  practice  of  roads  as  to  the  succession 
of  authority  among  the  higher  officials  of  the  road,  there  is  a  very 
general  agreement  in  placing  the  immediate  supervision  of  the 
track  for  each  division  of  approximately  one  hundred  miles  under 
a  man  known  as  roadmaster  or  perhaps  supervisor.  Some  roads 
extend  the  authority  of  the  roadmaster  over  a  greater  length  of 
road  and  then  appoint  "supervisors"  who  individually  control 
shorter  lengths  and  who  report  to  the  roadmaster.  The  supervisor 
of  each  minor  division  superintends  the  Avork  of  the  several  section 
gangs  in  his  division. 

The  roadmasters  usually  report  to  a  division  engineer,  but 
except  in  matters  of  exceptional  importance  or  which  may  involve 
new  methods  of  work,  the  roadmaster  is  expected  to  do  his  routine 
work  without  special  orders  and  to  be  responsible  for  its  proper 

209 


198  RAILROAD  ENGINEERING 

execution.  The  roadmaster  should  be  thoroughly  conversant  with 
every  phase  of  the  work  done  under  him,  and  although  it  is  prefer- 
able that  he  should  have  come  up  from  the  ranks,  he  should  have 
a  far  better  education  than  is  possessed  by  the  large  majority  of 
track  laborers.  The  best  roadmasters  are  those  who  have  a  technical 
education  but  who  have  served  a  sufficient  time  in  the  ranks  to 
have  become  familiar  with  the  practical  details  of  track  work. 
The  Southern  Pacific  R.  R.  Co.  require  a  roadmaster  to  "pass 
over  the  entire  straight  portion  of  his  districts,  either  on  foot  or 
on  velocipede  cars,  at  least  twice  every  month,  and  over  that  por- 
tion in  canyons  and  in  the  mountains  at  least  three  times  per 
month."  He  should  have  the  work  of  the  entire  division  so  thor- 
oughly  mapped  out  in  his  mind  that  he  has  a  sufficiently  clear 
idea  of  the  condition  of  every  part  of  his  division  at  any  time  and 
thereby  save  himself  from  censure  due  to  any  neglect  of  the  track 
work  at  any  place. 

The  most  effective  way  to  do  this  is  to  have  the  section  fore- 
xaen  under  such  a  state  of  drill  that  there  will  be  no  failure  to 
remedy  any  slight  defect  or  report  a  greater  one.  The  roadmaster 
must  rely  on  his  discipline  of  the  section  foremen  rather  than  on 
his  personal  observation,  although  he  should  not  relax  any  effort 
to  make  his  personal  observations  as  thorough  as  possible. 

The  section  foreman  should  generally  be  a  man  who  has  served 
his  time  as  a  track  laborer,  but  he  should  also  be  a  man  who  has 
sufficient  education  and  intelligence  to  make  out  reports  and  cor- 
rectly interpret  plans  and  tabular  statements.  Another  absolutely 
essential  quality  is  an  ability  to  control  men  without  violence  or 
abuse.  He  should  not  only  thoroughly  understand  all  the  details 
of  maintaining  a  track  in  condition,  but  should  be  able  to  repair  a 
track  and  make  it  safe  for  trains  in  any  ordinary  emergency  such 
as  a  broken  rail,  a  washout,  or  a  tearing  up  of  the  track  due  to  a 
wreck.  He  should  familiarize  himself  with  all  rules  of  the  road 
regarding  train  running  with  which  he  may  ever  be  immediately 
concerned,  and  also  with  all  rules  and  standards  of  track  construc- 
tion which  may  have  been  adopted.  The  last  qualification,  which 
is  becoming  more  and  more  essential,  raises  the  standard  for  sec- 
tion foremen  above  what  was  formerly  considered  necessary. 


RAILROAD  ENGINEERING  199 

Many  roads  require  (by  their  rules)  that  the  foreman  shall 
take  part  in  the  manual  labor  of  the  gang.  The  wisdom  of  this 
rule  depends  somewhat  on  the  work  being  done  and  on  the  num- 
ber of  men  in  the  gang.  If  there  are  as  many  as  eight  laborers  in 
the  gang,  the  foreman  may  have  all  he  can  do  in  directing  them. 
It  is  frequently  advantageous  to  have  the  men  work  in  pairs,  and 
when  the  work  is  light,  it  may  be  best  to  have  live  laborers  with 
the  foreman  in  a  gang,  and  then  the  foreman  may  work  with  the 
odd  man. 


RAILROAD  ENGINEERING 

PART  III 


ECONOMICS 


RAILROAD  FINANCES 

159.  Capitalization.  Practically  all  of  the  following  state- 
ments regarding  capitalization,  etc.,  of  the  railroads  of  the  country 
are  taken  from  the  reports  of  the  Interstate  Commerce  Commission 
and  may,  therefore,  be  considered  as  reliable  as  any  which  are  obtain- 
able. Many  of  the  following  figures  are  taken  from  the  report  for 
the  year  ending  June  30,  1912.  At  that  time  the  capital  stock 
was  given  as  $8,622,400,821.  Disregarding  the  fractions  of  mil- 
lions, the  funded  debt,  expressed  in  millions,  was  11,130,  or  a  total 
capitalization  of  19,752  million  dollars.  This  represents  approxi- 
mately one-tenth  of  the  national  wealth.  The  "investment  in  road 
and  equipment",  to  June  30,  1912,  was  stated  as  16,004  millions. 
Unfortunately  the  finances  of  railroads  have  been  so  manipulated 
that  any  statement  of  "cost  of  road"  does  not  usually  represent 
the  capital  actually  spent  on  construction. 

The  above  figures  apply  to  237,467  miles  of  line,  the  total 
mileage  being  nearly  247,000  miles.  The  railroads  directly  employed 
1,716,380  employes,  to  whom  they  paid  over  $1,252,000,000, 
which  was  over  44  per  cent  of  the  operating  revenues,  amounting  to 
more  than  $2,842,000,000.  The  employes  represent  a  population  of 
perhaps  eight  millions  who  are  directly  dependent  on  the  railroads 
for  support.  Considering  the  industries,  such  as  locomotive  and 
car  shops,  which  depend  entirely  on  railroads  for  business,  and  also 
the  industries,  such  as  steel  mills  and  bridge  works,  which  have 
railroads  as  their  largest  customers,  it  may  perhaps  be  estimated 
that  one-fourth  of  the  entire  population  of  the  country  are  directly 
or  indirectly  dependent  for  their  support  on  railroads. 

If  the  argument  is  carried  still  further  and  the  fact  is  recog- 
nized that  a  very  large  proportion  of  the  products  of  agriculture, 

213 


202  RAILROAD  ENGINEERING 

mines,  and  manufactories  could  not  otherwise  be  transported  to 
consumers,  or  would  not  be  utilized  and,  therefore,  would  not  be 
produced,  the  debt  of  the  country  to  railroad  transportation  may 
be  better  appreciated. 

Although  the  stocks  and  bonds  of  many  of  the  smaller  rail- 
roads are  owned  by  large  corporations  in  their  corporate  capacity, 
yet  of  the  total  of  19,752  millions  of  stocks  and  bonds  outstanding 
in  1912,  13,986  millions,  or  about  71  per  cent,  were  owned  by  ''other 
than  railroad  corporations" — chiefly  private  investors.  On  the 
basis  of  total  assets  of  19,752  million  dollars  and  an  estimated 
population  of  95,172,000  people,  the  average  ownership  is  over 
$207  per  head  of  population.  The  total  operating  revenue  of  over 
$2,842,000,000  represents  an  average  payment  of  nearly  $30  per 
inhabitant,  for  the  year.  The  "number  of  passengers  carried  one 
mile"  was  33,132,000,000,  which  means  that  the  average  passenger 
traveled  348  miles  during  the  year.  The  average  number  of  pas- 
sengers on  a  train  was  53  and  they  traveled  an  average  journey 
of  33.18  miles. 

The  "number  of  tons  of  freight  carried  one  mile"  was 
264,080,000,000,  which  means  that  the  average  inhabitant  supplied 
a  freight  business  equivalent  to  moving  2775  tons  one  mile,  or 
moving  one  ton  2775  miles,  or  moving  50  tons  55  miles.  As  an  aid 
to  grasping  this  perhaps  incredible  statement  combined  with  the 
statement  of  an  average  annual  payment  of  $30  per  inhabitant,  it 
should  be  remembered  that  whenever  a  ton  of  coal  or  even  a  pound 
of  sugar  is  bought,  the  price  paid  includes  payment  made  to  a  rail- 
road company  for  freight. 

While  the  above  figures  must  be  considered  simply  as  aver- 
ages, and  not  necessarily  applicable  to  any  one  road,  they  give  some 
idea  of  the  magnitude  of  railroad  business  and  what  the  average 
railroad  may  be  expected  to  do.  Considering,  however,  that  the 
great  railroads  of  the  country  are  already  built,  and  that  the  roads 
yet  to  be  built  will  probably  be  of  minor  importance,  even  such 
an  average  statement  could  hardly  apply  to  any  new  enterprise 
except  with  a  very  large  discount. 

160.  Stocks  and  Bonds.  An  ordinary  mercantile  business, 
or  even  an  ordinary  factory  is  conducted  on  the  capital  directly 
furnished   by  the   owner   or  owners.    Therefore   any  profit  over 

214 


RAILROAD  ENGINEERING  203 

the  operating  expenses  may  be  applied  as  dividends  no  matter 
how  small  the  percentage.  Very  few  of  the  railroads  of  this  country 
have  been  constructed,  even  approximately,  on  this  basis.  Usually 
a  large  part  of  the  virtual  ownership  of  a  railroad  is  represented 
by  bonds.  The  limit  of  the  issue  of  the  bonds  may  be  that  which 
expresses  the  confidence  of  the  public  in  the  enterprise,  or,  in  other 
words,  the  value  which  it  is  assumed  that  the  whole  property  could 
be  sold  for  under  a  foreclosure  sale. 

During  the  early  history  of  railroading,  when  railroads  were 
being  run  through  well-established  communities  which  were  with- 
out railroad  facilities,  the  success  of  the  enterprises  seemed  so 
certain  that  little  or  no  difficulty  was  experienced  in  borrowing 
on  bonds  capital  sufficient,  and  even  more  than  sufficient,  to  construct 
and  equip  the  road  complete.  But  such  opportunities  are  practically 
past.  The  capital  stock  actually  paid  in  represents  the  margin, 
or  the  uncertainty  between  what  it  actually  will  cost  to  build  the 
road  and  its  estimated  foreclosure  value.  The  nominal  issue  of 
stock  is  usually  about  equal  to  the  issue  of  bonds.  In  1912,  the 
ratio  was  86  to  1 1 1 . 

At  its  best,  the  inception  of  such  an  enterprise  means  a  con- 
siderable outlay  of  money.  A  group  of  men,  acting  on  the  belief 
that  a  road  passing  through  certain  towns  will  be  a  profitable  enter- 
prise, forms  a  temporary  organization,  develops  the  enterprise,  has 
surveys  made,  and  then  if  the  developed  plans  still  look  encouraging, 
has  bonds  engraved  and  placed  on  the  money  market  for  sale, 
usually  through  a  financial  syndicate.  Even  if  it  were  possible 
to  raise  enough  money  for  actual  construction,  the  amount  of  money 
required  for  this  preliminary  work,  although  but  a  small  percentage 
of  the  gross  amount  required,  is  sometimes  a  large  sum  of  money. 

The  gross  amount  required  is  increased  by  the  frequently 
ignored  fact  that  a  road  does  not  attain  its  "normal"  traffic  for 
five  or  ten  years  after  it  begins  operation,  and  unless  it  has  sufficient 
funds  as  "working  capital"  to  tide  over  the  initial  period  when  it 
does  not  perhaps  pay  operating  expenses,  it  is  very  apt  to  go  into 
the  hands  of  a  receiver. 

Stocks  and  bonds  may  therefore  be  considered  as  representing 
two  forms  of  ownership.  The  interest  on  the  bonds  is  a  lien  on 
the  receipts,  after  the  operating  expenses  have  been  paid.     Such 

215 


204  RAILROAD  ENGINEERING 

interest  must  be  paid  in  full  before  any  dividends  on  stock  may  be 
paid.  The  security  of  the  bonds  is  therefore  comparatively  good, 
and  the  profit  comparatively  certain  although  it  is  small. 

On  the  other  hand,  the  stocks  are  much  more  speculative.  No 
dividends  are  paid  until  the  operating  expenses  and  the  bond  interest 
are  fully  paid;  and  if  the  latter  is  not  paid,  the  bondholders  have 
a  right  to  demand  that  a  "receiver"  be  appointed  and  if  necessary 
that  the  road  be  sold.  Since  such  a  sale  will  not  usually  realize 
more  than  the  face  value  of  the  bonds  (and  sometimes  not  even 
that),  the  stockholders  may  lose  their  entire  investment.  But  if 
the  road  makes  money,  the  excess  which  may  be  allowed  for  divi- 
dends may  be  a  very  large  return  on  the  amount  of  capital  actually 
"paid  in.  It  may  very  easily  be  shown  that  a  comparatively  small 
change  in  the  amount  of  business  done  may  suffice  to  change  a 
good  profit  for  the  stockholders  into  an  actual  deficit,  which  makes 
a  receivership  dangerously  probable. 

The  relative  profit  on  stocks  and  bonds  and  the  fact  that  rail- 
road securities,  although  sometimes  very  profitable,  are  very  pre- 
carious in  value  is  shown  by  the  following  statements:  The  year 
ending  June  30,  1902,  was  the  best  year  (up  to  that  time)  ever 
known  in  the  railroad  business.  But,  in  spite  of  this,  44.6  per 
cent  of  all  railroad  stocks  then  in  existence  paid  no  dividends. 
The  average  rate  paid  on  dividend-paying  stock  was  only  5.55  per 
cent.  Even  granting  that  much  of  railroad  stock  is  "watered" — 
which  means  essentially  that  it  represents  little  or  no  cash  actually 
paid  in — the  fact  remains  that  during  that  year  44.6  per  cent  of 
all  the  stock  issued  paid  no  dividends.  From  1895  to  1897,  over 
70  per  cent  of  all  railroad  stocks  paid  no  dividends. 

Th^  record  regarding  bonds  is  much  better,  the  percentage  of 
the  entire  bond  issue  which  failed  to  pay  anything  during  1901-2 
being  less  than  5  per  cent.  While  it  is  true,  almost  without  excep- 
tion, that  a  railroad  builds  up  the  section  of  country  through  which 
it  passes  and  increases  its  value  far  beyond  the  cost  of  the  road, 
yet  it  is  also  true  that  very  few  roads  which  are  old  enough  to 
have  a  history  have  escaped  a  receivership  at  some  time  in  their 
growth,  even  though  they  may  now  be  gilt-edged  properties. 

161.  Gross  Revenue.  The  estimation  of  the  probable  volume 
of  traffic  or  the  gross  revenue  of  a  proposed  road  can  only  be  approx- 

216 


RAILROAD  ENGINEERING  205 

imated  at  best  and  even  this  requires  experience.  Since  it  requires 
five  years  or  more  for  a  road  to  attain  its  normal  traffic,  investors 
should  not  be  disappointed  when  the  returns  for  the  first  few  years 
are  less  than  those  anticipated. 

The  ouly  practicable  method  of  estimating  traffic  is  to  study 
the  resources  of  the  belt  of  country  which  will  be  tributary  to  the 
proposed  line,  estimating  the  business  obtainable  from  every  factory, 
mine,  blast  furnace,  farm,  village,  etc.  When,  as  is  usual,  the 
line  passes  through  or  reaches  cities  which  are  already  supplied 
with  railroad  facilities,  the  detailed  computation  of  business  becomes 
very  uncertain.  But  if  the  chief  business  of  the  road  is  to  develop 
local  business  along  a  route  which  has  no  other  means  of  com- 
munication, then  the  computation  is  easier.  The  two  dangers 
in  the  method  lie  in  the  entire  neglect  to  allow  for  certain  important 
sources  of  income  and,  on  the  other  hand,  to  overestimate  the 
income  from  a  certain  source.  Analogous  to  the  last  is  the  neglect 
to  allow  for  present  or  future  competition,  which  may  practically 
cut  off  sources  of  income. 

Although  some  idea  of  the  product  of  factories  and  mines 
may  be  obtained  from  records  as  to  their  present  or  prospective 
output,  the  income  from  passenger  business  can  only  be  computed 
from  comparisons  with  other  roads.  The  freight  business  is  gen- 
erally two-thirds  of  the  business  of  a  road,  except  on  those  roads 
which  have  an  enormous  suburban  traffic.  The  average  receipts 
per  passenger  mile  are  about  2  cents,  but  it  is  the  enormous  com- 
muter business  and  the  growth  of  traVel  on  1000-mile  tickets  which 
bring  down  the  average  to  this  figure  from  the  usual  charge  of 
3  cents  per  mile  and  the  even  higher  charges  on  roads  with  light 
traffic  and  very  heavy  expenses. 

As  a  rough  check  on  the  above  method  the  annual  reports 
of  the  Interstate  Commerce  Commission  give  the  gross  earnings 
from  operation  for  the  road  in  each  of  three  sections  into  which  the 
country  has  been  divided.  Dividing  this  gross  value  by  the  popu- 
lation of  the  section  (which  is  deducible  from  the  report)  an  average 
value  per  head  of  population  for  that  section  is  obtainable.  The 
value  for  the  whole  United  States  is,  as  previously  stated,  nearly 
$30,  but  the  value  for  some  one  section  may  prove  quite  different 
from   this.     Multiplying   the   value   obtained   by   the   population 

217 


206  RAILROAD  ENGINEERING 

which  may  be  considered  as  tributary  to  the  route  of  the  road, 
we  have  a  very  approximate  value  for  the  income  of  the  road.  The 
two  obvious  weaknesses  of  the  method  are  that  the  receipts  of 
the  proposed  road  may  prove  very  different  from  the  average  for 
that  section  and  also  that  the  computation  of  the  tributary  popu- 
lation is  a  very  uncertain  calculation.  But  since  the  method  may 
be  easily  tried,  it  furnishes  a  check  of  some  value. 

As  a  better  check  there  are  usually  one  or  more  roads  which 
may  be  selected  which  have  substantially  the  same  characteristics 
and  whose  incomes  per  mile  of  road  are  nearly  equal  and  which  sup- 
posedly equal  the  expected  income  of  the  proposed  line.  Assum- 
ing the  existence  of  such  roads  and  that  the  engineer  has  sound 
judgment  in  estimating  their  characteristics,  this  method  should 
be  employed  if  possible,  at  least  to  check  the  value  of  any  other 
computation. 

The  number  of  passengers  per  train  is  of  course  very  uncertain. 
The  average  number  of  passengers  carried  for  each  passenger-train- 
mile,  as  previously  stated,  was  53,  which  is  less  than  a  car  load. 
And  when  it  is  considered  that  even  this  average  includes  the  heavy 
traffic  roads  and  the  well-filled  trains  on  suburban  roads,  the  average 
number  on  a  light-traffic  road  must  be  very  small.  The  number 
of  passenger  trains  per  day  bears  but  little  relation  to  the  number 
that  can  be  carried  in  one  train  load — as  the  above  (53)  shows. 

The  passenger  business  must  be  developed,  coaxed,  and  encour- 
aged, which  can  only  be  done  by  a  frequency  of  service  which  is 
usually  far  ahead  of  the  requirements  from  a  mere  hauling  stand- 
point. It  is  a  very  poor  road  which  cannot  afford  two  passenger 
trains  per  day  each  way.  The  total  number  of  passengers  carried 
might  not  suffice  to  fill  one  car,  but  it  would  probably  be  a  far 
greater  number  than  would  be  hauled  if  there  were  only  one  train 
per  day.  The  criterion  for  an  increase  in  number  would  appear 
to  be  as  follows: 

When  it  may  be  shown  that  the  increase  in  facilities  due  to 
an  additional  train  will  so  encourage  traffic  that  the  additional 
receipts  will  equal  or  exceed  the  cost  of  the  additional  train  (which 
will  be  less  than  the  average  cost  per  train-mile),  then  the  added 
train  will  evidently  be  justified. 

The  average  revenue  per  passenger-train-mile  for   1912  was 

218 


RAILROAD  ENGINEERING  207 

given  as  $1.29,  which  includes  receipts  from  mail  and  express,  as 
well  as  passenger  receipts.  The  average  receipts  per  freight-traiii- 
mile  was  $3.02,  or  more  than  twice  as  much,  and  this,  in  spite 
of  the  fact  that  a  passenger,  weighing  perhaps  150  pounds,  paid 
1.987  cents  per  mile,  while  a  ton  of  freight  paid  0.744  cent  per 
mile.  This  great  difference  is  partly  due  to  the  fact  that  the 
ratio  of  dead  load  to  live  load  in  freight  is  about  1 : 2,  but  on  pas- 
senger trains  it  may  be  5  : 1  or  even  10  : 1.  Another  reason  is 
that  freight  trains  are  made  up,  if  possible,  so  that  each  engine  is 
hauling  about  the  limiting  number  of  cars  that  it  can  handle  (so 
as  to  reduce  the  number  of  trains  required)  while,  as  stated  above, 
passenger  trains  are  run  frequently,  and  light,  so  as  to  encourage 
the  passenger  traffic. 

162.  Monopoly  in  Railroad  Business.  One  danger  to  be 
considered  in  the  estimating  of  gross  revenue,  and  also  in  the  sub- 
sequent designing  of  the  road  and  in  the  facilities  offered  for  traffic, 
is  the  assumption  that  the  road  "will  have  all  the  traffic  there  is". 
Even  ignoring  the  effect  of  possible  future  competition,  which 
may  be  encouraged  and  somewhat  developed  by  a  marked  lack 
of  facilities  on  an  existing  road,  it  should  be  recognized  that  a  large 
part  of  the  traffic  depends  directly  on  the  facilities  offered.  A 
factory's  very  existence  depends  on  its  ability  to  collect  its  raw 
material,  manufacture  it,  and  deliver  it  at  the  door  of  the  average 
consumer,  perhaps  in  a  distant  city,  as  cheaply  as  other  manu- 
facturers of  the  same  article.  Under  close  competition,  an  increase 
in  one  single  item  of  expense,  such  as  cartage  from  the  factory  to 
the  railroad,  may  make  up  the  difference  between  profit  and  loss. 

The  ideal  location  for  a  railroad  is  that  it  shall  pass  through 
the  heart  of  the  manufacturing  district  of  any  city  and  that  its 
passenger  station  shall  be  located  in  the  immediate  neighborhood 
of  the  business  center  of  the  city.  The  purchase  of  such  property 
for  tracks  and  stations  after  the  city  is  well  established  is  of  course 
very  expensive,  but  the  disadvantages  of  a  location  which  is  con- 
siderably removed  from  the  ideal  location  are  very  great.  These 
disadvantages  are  so  increased  under  competition  that  a  road's 
traffic  may  be  practically  ruined.  Even  the  passenger  business  is 
greatly  affected.  The  passengers  who  will  travel  anyway  regard- 
less of  inconveniences  are  comparatively  few. 

219 


208  RAILROAD  ENGINEERING 

The  most  important  practical  feature  of  this  question  Hes  in 
the  fact,  referred  to  before,  that  the  margin  between  profit  and 
loss  is  very  small,  that  a  very  large  proportion  of  the  gross  revenue 
must  be  paid  out  for  operating  expenses,  that  nearly  all,  if  not  quite 
all,  of  the  remainder  goes  to  pay  interest  on  the  bonds  and  only 
a  small,  doubtful  percentage  remains  for  dividends.  Therefore,  the 
dividends  come  literally  from  the  unnecessary  traffic  which  must  be 
coaxed  and  which  will  not  travel  on  a  road  which  lacks  conveniences. 

The  force  of  this  may  be  seen  still  more  by  considering  the 
easy  financial  condition  of  a  well-established  road.  The  receipts 
are  large  and  are  partly  spent  in  creating  still  further  conveniences, 
commodious  and  convenient  stations,  better  rolling  stock,  etc. 
These  in  turn  encourage  more  traffic,  which  still  further  increases 
receipts,  until  there  seems  to  be  no  end  to  the  financial  ability 
of  the  road.  Such  roads  are  the  Pennsylvania,  the  New  York 
Central,  and  some  others.  On  the  other  hand,  the  poverty  of 
a  road  begets  a  poverty  of  service  which  still  further  decreases 
receipts  until  ruin  is  in  sight.  Many  a  road  has  been  practically 
compelled  to  supply  free  cartage  for  freight  (or  allow  for  it  by  a 
rebate)  to  compensate  for  an  inconvenient  freight  station.  Since 
the  Interstate  Commerce  regulations  now  prevent  rebates,  rail- 
roads having  inconvenient  locations  for  stations  or  terminals  do 
not  have  even  that  method  of  compensating  their  handicaps.  The 
enormous  sums  paid  to^bring  passenger  terminals  into  the  heart  of 
a  great  city  are  instructive  examples  in  this  respect. 

163.  Division  of  Gross  Revenue.  Of  the  more  than  2000 
railroad  corporations^  listed  by  the  Interstate  Commerce  Com- 
mission, a  very  large  number  of  them  are  so  merged  with  the 
corporations  operating  them  that  their  separate  existence  is  only 
evident  on  paper.  The  capital  stock  of  many  of  them  is  partially 
or  entirely  owned  by  the  operating  company  and  they  are  operated 
under  a  great  variety  of  leases,  etc.  It  is  therefore  difficult  to 
obtain  from  the  financial  statement  of  any  of  the  large  corpora- 
tions the  division  of  gross  revenue.  The  following  case  is^^fairly 
typical  of  a  simple,  independent  railroad  corporation:     '«"vb>8«ih 

It  is  an  independent  road  371  miles  long,  with  a  capitMl- Bt6ck 
of  $1,114,400  and  a  funded  debt  of  $9,415,000,  which  is  madfe  up 
of  bonds  to  the  amount  of  $8,555,000  and  "equipment  trust ^bli- 

220 


RAILROAD  ENGINEERING  209 

gations"  to  the  amount  of  S860,000.  This  is  evidently  a  case  of 
a  road  built  chiefly  on  the  proceeds  of  the  bonds,  the  issue  of  stock 
being  quite  small.  The  gross  fevenue  for  1901-1902  was  SI ,708,937. 
Of  this,  $1,101,884  or  64.5  per  cent  was  spent  in  operating  expenses. 
Of  the  remainder,  $552,821  or  32.4  per  cent  was  needed  for  the 
''fixed  charges".  This  left  only  $54,232  available  for  anything 
else.  Although  this  amounted  to  nearly  5  per  cent  on  the  rather 
small  issue  of  capital  stock,  no  dividend  was  declared.  It  was 
evidently  preferred  to  add  this  amount  to  their  working  capital 
or  perhaps  to  use  it  in  improvements.  Such  an  action  is  virtually 
the  reinvestment  of  profits  for  the  improvement  of  the  road. 

The  complication,  due  to  the  corporate  ownership  of  railroad 
stocks  and  bonds,  as  well  as  other  income-bearing  property,  by 
railroad  corporations,  makes  it  impossible  to  analyze  the  financial 
statements  of  most  railroad  companies  as  easily  as  has  been  done 
above.  A  disbursement  item  by  one  corporation  is  an  income 
item  for  another  corporation.  The  Interstate  Commerce  Commis- 
sion publishes  each  year  a  statement  which  analyzes  the  reports 
of  all  the  roads  of  the  country  and  considers  them  as  one  system, 
which  is  done  by  eliminating  all  but  the  net  balance  of  all  inter- 
corporate payments.     Some  of  the  items  of  the  statement  for  the 

year  ending  June  30,   1912,  are  as  follows: 

(Millions) 

Operat  ing  revenues  (rail  operations) $2,842, 

Operating  expenses  (rail  operations) 1,972, 

Total  net  revenue  (adding  a  million  from  "outside  operations") 871, 

Taxes  accrued 120, 

Operating  income 751, 

Other  income  (chiefly  dividends  and  interest  on  stocks  and  securities 

owned) 89, 


Gross  income 840, 

Deductions  from  gross  income  (chiefly  interest  on  funded  debt  and  net 

intercorporate  balances) 488, 

Net  corporate  income  for  year 352, 

Adding  balance  of  profit  and  loss,  June  30,  1911 1>124, 


Gross  surplus,  June  30,  1912 1,477, 

Net  loss  during  year  (from  "adjustments,  through  profit  and  loss") ....  30, 

Surplus  available  for  appropriation 1,447, 

Net  dividends  declared  during  year $299, 

Appropriations  for  extensions  and  betterments $  53,  352, 


Balance,  carried  to  general  balance  sheet $1,095, 


221 


210  RAILROAD  ENGINEERING 

Although  it  may  appear  ultraconservative  to  have  allowed 
dividends  of  only  299  millions  when  the  "surplus  available  for 
appropriation"  was  nearly  five  times  that  amount,  it  should  also 
be  noted  that  the  net  balance  carried  over  was  but  little  over  one- 
half  of  the  annual  operating  expenses.  The  balance,  after  paying 
interest  charges  for  the  year,  would  not  run  the  roads  four  months 
if  all  income  were  cut  off.  While  this  is  an  inconceivable  contin- 
gency, the  margin  for  working  capital  is  none  too  large.  Even 
this  margin  was  reduced  30  millions  during  the  year. 

164.  Fixed  Charges.  The  fixed  charges  of  a  simple  railway 
corporation  which  operates  only  the  line  which  it  owns  will  consist 
chiefly  of  the  interest  on  its  bonds.  Besides  this  there  may  be 
the  interest  on  "equipment  trust  obligations"  which  are  merely  a 
particular  form  of  bond  issued  to  pay  for  equipment  needed  by 
the  road.  Another  item  will  be  the  interest  on  sundry  interest- 
bearing  current  habihties;  this  is  generally  but  a  small  percentage 
of  the  fixed  charges,  but  the  current  liabilities  are  often  made  to 
disappear  by  a  new  issue  of  bonds  which  take  up  an  old  issue  and 
at  the  same  time  cover  all  floating  liabilities. 

The  complicated  financial  relations  existing  between  operating 
roads  and  their  leased  lines  introduces  some  other  items  which  are 
entered  under  fixed  charges.  One  of  these  items,  which  is  always 
less  than  1  per  cent  of  the  total  fixed  charges,  is  called  "salaries 
and  maintenance  of  organization".  These  refer  to  the  salaries 
which  are  paid  to  a  few  of  the  general  officers  of  a  leased  road  who 
are  retained  to  continue  such  work.  Another  item  is  placed,  when 
it  occurs,  among  the  fixed  charges;  this  is  the  rental  paid  for  a  leased 
road.  As  this  is  an  "intercorporate"  payment,  it  did  not  appear 
in  the  above  general  summary  for  the  roads  of  the  United  States, 
nor  did  it  appear  in  the  detailed  statement  of  the  road  previously 
described,  since  that  road  had  no  leased  lines. 

165.  Net  Revenue.  The  net  revenue  is  that  which  remains 
after  the  operating  expenses  and  fixed  charges  have  been  paid.  In 
general  it  is  available  for  dividends,  but  practically  a  very  consid- 
erable proportion  of  it  will  be  devoted  to  improvements  or  to  the 
accumulation  of  a  surplus  which  will  serve  as  "working  capital". 
During  the  year  1911-12,  34.57  per  cent  of  railroad  stock  paid  no 
dividends,  although  the  case  quoted  above  is  but  one  of  many  in 

222 


RAILROAD  ENGINEERING  211 

which  there  was  a  considerable  surpkis  after  paying  the  operating 
expenses  and  fixed  charges.  Dividends  of  less  than  4  per  cent 
were  paid  on  2.67  per  cent  of  stock. 

This  small  proportion  shows  the  tendency  to  pass  the  dividend 
unless  it  may  be  made  larger.  About  49  per  cent  of  the  stock 
paid  dividends  varying  from  4  to  8  per  cent.  This  represents 
the  bulk  of  the  stock  paying  normal  dividends.  Smaller  percentages 
of  the  stock  paid  higher  rates.  On  8.43  per  cent  of  stock,  dividends 
of  10  per  cent  and  over  were  paid.  Of  course  this  last  represents 
roads  which  are  short  and  very  exceptional  in  character.  It  should 
also  be  kept  in  mind  that  the  percentages  of  dividend-paying  stock 
quoted  above  are  almost  the  highest  of  any  in  the  history  of 
railroading.  If  general  railroad  conditions  should  ever  return  to 
those  existing  in  1896,  when  over  70  per  cent  of  all  the  stocks  paid 
no  dividends,  railroad  stock  would  be  less  attractive  for  investment 
than  now  in  spite  of  the  abnormal  profits  which  are  occasionally 
realized. 

166.  Operating  Expenses.  Uniformity  per  Train-Mile.  The 
classification  of  operating  expenses  here  adopted  will  follow,  both  in 
general  and  in  detail,  the  classification  used  by  the  Interstate  Com- 
merce Commission.  The  figures  given  will,  in  general,  be  averages. 
This  is  further  justified  by  the  very  remarkable  fact  that  the  expenses 
per  tram-mile  are  nearly  constant,  whether  the  trains  be  few  or 
many,  heavy  or  light.  Of  course  there  are  very  numerous  excep- 
tions to  this  rule,  but  it  will  generally  be  found  that  the  marked 
exceptions  apply  to  very  short  roads  which  either  have  abnormal 
traffic  or  have  peculiar  financial  relations  with  a  parent  company 
which  is  operating  it. 

The  report  for  1901-2  shows  that  the  ten  greatest  railroads 
of  the  country,  each  operating  more  than  4000  miles  of  road,  spent 
SI.  167  per  train-mile.  The  average  for  the  whole  United  States  was 
$1.1796.  It  should  also  be  noted  that  the  ratio  of  total  operating 
expenses  to  total  receipts  from  operations  was  59.78  per  cent  for 
the  ten  roads  and  64.66  per  cent  for  the  whole  United  States.  To 
judge  of  the  operating  expenses  of  smaller  roads,  the  figures  for 
No.  10,  Table  XIV,  were  taken  from  the  report,  the  selections  being 
made  at  random  except  that  the  lengths  were  all  less  than  100  miles 
and  all  of  the  roads  were  "operating  roads  independent". 

223 


212 


RAILROAD  ENGINEERING 

TABLE  XIV 
Operating  Expenses 


Ratio  of  Total  Operating  Expenses 

No. 

Length 

Operating  Expenses 

TO  Total  Receipts  from  Operation 

(miles) 

PER  Train-Mile 

(per  cent) 

1 

21.25 

$0.70621 

71.62 

2 

32.60 

0.47828 

64.21 

3 

31.00 

0.60649 

96.12 

4 

64.10 

0.90588 

43.41. 

5 

42.00 

0.54323 

63.07 

6 

61.00 

0.75357 

81.05 

7 

50.00 

0.87456 

90.32 

8 

50.39 

2.07044 

97.58 

9 

70.78 

1.02854 

53.46 

10 

52.20 

1.74952 

62.15 

Average 

$0.97167 

72.30 

10  longest  roads 

1.167 

59.78 

Whole  U.  S. 

1 . 17960 

64.66 

A  little  study  of  the  above  figures  will  show,  as  might  be 
expected,  that  local  conditions  will  so  affect  a  very  small  road  that 
its  operating  expenses  per  train-mile  may  be  considerably  more 
or  considerably  less  than  the  average.  The  average  value  for  the 
ten  short  roads  here  chosen  is  less  than  the  average  for  the  United 
States,  and  although  two  of  the  ten  are  much  greater  than  the 
average,  it  is  found  that  the  average  value  for  short  roads  is  a  little 
less  rather  than  more. 

The  reasons  for  the  uniformity  are  not  difficult  to  understand. 
Although  the  gross  expense  of  any  one  item  (such  as  rail  renewals) 
for  a  large  road  is  enormously  greater  than  the  same  item  for  a 
small  road,  the  divisor  (the  number  of  trains)  is  correspondingly 
greater  and  the  quotient,  which  is  the  expense  for  that  item  per 
train-mile,  is  substantially  uniform. 

Average  Cost  of  a  Train^Mile.  The  increase  in  the  average 
cost  of  a  train-mile  is  shown  in  Table  XV,  which  gives  the  average 
cost  of  operating  a  train  1  mile  during  23  consecutive  years.  The 
nearly  uniform  growth  of  over  73  per  cent  between  1895  and  1912 
is  very  significant.  While  predictions  of  future  cost  are  necessarily 
guesswork,  estimators  in  railroad  economics  must  make  the  best 
possible  predictions  for  five  or  ten  years  ahead.  There  seems  to  be  no 


224 


RAILROAD  ENGINEERING 

TABLE  XV 
Average  Cost  of  Operating   a  Train  1  Mile 

(All  roads  in  U.  S.) 


213 


Year 

Cents 

Year 

Cents 

Year 

Cents 

Year 

Cents 

1890 

96.006 

1896 

93 . 838 

1902 

117.960 

1908 

147.340 

1891 

95.707 

1897 

92.918 

1903 

126.604 

1909 

143 . 370 

1892 

96.580  . 

1898 

95.635 

1904 

131.375 

1910 

148.865 

1893 

97 . 272 

1899 

98.390 

1905 

132.140 

1911 

154.338 

1894 

93.478 

1900 

107.288 

1906 

137.060 

1912 

159.077 

1895 

91.829 

1901 

112.292 

1907 

146.993 

reason  to  hope  for  a  decrease  in  the  rate  or  to  expect  anything  else 
than  a  continued  increase,  even  though  it  may  prove  less  rapid 
than  heretofore. 

167.  Classification  of  Operating  Expenses.  In  Table  XVI  is 
shown  the  classification  adopted  by  the  Interstate  Commerce  Com- 
mission— the  total  cost  for  each  item,  each  item's  per  cent  part  of 
the  total,  and  the  cost  in  cents  per  train-mile,  which  is  found  by 
multiplying  each  percentage  by  the  average  cost  per  train-mile  for 
that  year  ($1.59077,  or  159.077  cents).  While  these  averages  are 
very  instructive  in  giving  a  broad  view  of  the  subject,  they  must  be 
used  cautiously.  For  example,  the  fuel  required  per  mile  for  loco- 
motives is  a  very  variable  quantity,  depending  on  the  size  of  the 
locomotive  and  the  amount  of  work  done,  and  it  would  be  very 
foolish  to  make  any  calculations  on  the  basis  that  the  cost  of  fuel 
per  locomotive-mile  would  be  exactly  16.27  cents. 

168.  Maintenance  of  Way  and  Structures.  The  cost  of  ties 
is  the  largest  single  item  for  track  material;  the  cost  per  train-mile 
has  nearly  doubled  since  1895.  This  has  been  due  to  a  combination, 
in  varying  proportions,  of  three  causes — (a)  increased  cost  of  ties; 
(b)  lowering  of  quahty  to  pass  inspection,  due  to  growing  scarcity; 
and  (c)  increase  in  train  load  and  concentrated  wheel  load,  resulting 
in  more  rapid  deterioration.  There  seems  to  be  no  chance  of  decrease 
in  cost  in  the  future  unless  possibly  by  more  effective  preservative 
processes  or  by  the  invention  of  a  metal  or  a  steel-concrete  tie  which 
shall  be  so  durable  that,  in  spite  of  increased  first  cost,  it  is  cheaper 
per  train-mile. 

The  cost  of  roadway  and  track  (item  6)  is  the  labor  of  track 


225 


214 


RAILROAD  ENGINEERING 


TABLE  XVI 

Analysis  of  Operating  Expenses  of  all  Railroads   in  the  United  States 

for  Year  Ending  June  30,  1912,  Showing  Percentage  of  Each 

Item  to  Total  and  Cost  in  Cents  per  Train=Mile 


Total 

Per  Cent 

Cents  per 

Item 

Account 

Amount 

OF  Total 

Train- 

No. 

(thousands) 

Expenses 

Mile 

MAINTENANCE  OF  WAY  AND 

STRUCTURES 

1 

Superintendence 
Ballast 

$18,789, 

0.990 

1.58 

2 

7,157, 

0.377 

.60 

3 

Ties 

55,463, 

2.921 

4.65 

4 

Rails 

16,438, 

.866 

1.38 

5 

Other  track  material 

17,346, 

.914 

1.45 

6 

Roadway  and  track 

129,397, 

6.815 

10.84 

7 

Removal  of  snow,  sand,  and  ice 

6,920, 

.364 

.58 

8 

Tunnels 

1,141, 

.060 

.10 

9 

Bridges,  trestles,  and  culverts 

27,712, 

1.460 

2.32 

10-12 

Crossings,  all;  fences;  snow  structured 

8,066, 

.425 

.68 

13-15 

Signals,  telegraph,  electrical  power  trans- 

mission 

13,681, 

.720 

1.14 

16,17 

Buildings,  grounds,  docks,  wharves 

35,389, 

1.864 

2.96 

18 

Roadway  tools  and  supplies 

4,480, 

.236 

.38 

19 

Injuries  to  persons 

1,989, 

.105 

.17 

20,21 

Stationery,  printing,  and  other  expenses 

1,038, 

.054 

.09 

22,23 

Joint  tracks,  etc.  (net  balance) 

3,463, 

.182 

.29 

348,471, 

18.353 

29.20 

MAINTENANCE  OF  EQUIPMENT 

24 

Superintendence 

Repairs,  renewals,  and  depreciation: 
Locomotives,  steam  and  electric 

13,175, 

.694 

1.10 

25-30 

175,889, 

9.263 

14.74 

31-33 

Cars,  passenger 
Cars,  freight 

38,968, 

2.052 

3.26 

34-36 

183,968, 

9.690 

15.41 

37-39 

Equipment,  electrical,  car 

318, 

.017 

.03 

40-42 

Equipment,  floating 

1,333, 

.071 

.11 

43-45 

Equipment,  work 

6,128, 

.322 

.51 

46 

Equipment,  shop  (machinery  and  tools) 

10,418, 

.548 

.87 

47 

Equipment,  power  plant 

268, 

.014 

.02 

48 

Injuries  to  persons 

1,818, 

.096 

.15 

49,50 

Stationery,  printing,  and  other  expenses 

4,036, 

.213 

.34 

51,52 

Joint  equipment,  at  terminals  (net  bal- 

ance) 

676, 

.036 

.06 

436,995, 

23.016 

36.61 

TRAFFIC  EXPENSES 

53-60 

Agencies;  advertising;  fast  freight  lines; 

etc. 

59,047, 

3.110 

4.95 

226 


RAILROAD  ENGINEERING 
TABLE  XVI  (Continued) 


215 


Analysis  of  Operating  Expenses  of  all  Railroads  in  the   United  States 

for  Year  Ending  June  30,  1912,  Showing  Percentage  of  Each 

Item  to  Total  and  Cost  in  Cents  per  Train=Mile 


Total 

Per  Cent 

Cents  per 

Item 

Account 

Amount 

OF  Total 

Train- 

No. 

(thousands) 

Expenses 

Mile 

TRANSPORTATION  EXPENSES 

61,62 

Superintendence  and  train  dispatching 

$40,743, 

2.146 

3.41 

63 

Station  employes 

133,877, 

7.051 

11.22 

64-66 

Weighing;  car  service  association;   coal 

and  ore  docks 

15,949, 

.839 

1.33 

67-72 

Yards  (wages,  expenses,  supplies) 

116,781, 

6.151 

9.79 

73-76 

Yard  locomotives  (fuel,  water,  lubricants, 

supplies) 

33,658, 

1.773 

2.82 

77,  78 

\Operating  joint  tracks,  terminals,  yards, 
/     and  facilities  (net  balance) 

104,  105 

10,430, 

.550 

.88 

79,80 

Motormen  and  road  enginemen 

120,966, 

6.371 

10.14 

81 

Road  locomotives,  engine-house  expenses 

33,951, 

1.788 

2.84 

82 

Road  locomotives,  fuel 

194,142, 

10.225 

16.27 

83 

Road  locomotives,  water 

12,482, 

.657 

1.04 

84,85 

Road  locomotives,  lubricants,  and  other 

supplies 

7,430, 

.392 

.62 

86,87 

Operating    power    plants,     purchased 

power 

1,797, 

.095 

.15 

88 

Road  trainmen 

128,339, 

6.759 

10.75 

89 

Train  supplies  and  expenses 

34,462, 

1.815 

2.89 

90-92 

Interlockers,     signals,     flagmen,     draw- 

bridges 

17,831, 

.939 

1.49 

93 

Clearing  wrecks 

5,167, 

.272 

.43 

94-98 

Telegraph,  floating    equipment,  station- 

ery, miscellaneous 

20,009, 

1.054 

1.68 

99-103 

Loss  and  damage  to  property,  personal 

injuries 

56,838, 

2.994 

4.76 

984,852, 

51.871 

82.51 

GENERAL  EXPENSES 

106-116 

Salaries  of  general  officers,  clerks,  etc.; 
law,     insurance,      pensions,    miscella- 

neous 

69,297, 

3.650 

5.81 

Total  Operating  Expenses               $1,898,662, 

100.000 

159.08 

maintenance.  The  average  daily  wages  of  trackmen  have  increased 
almost  uniformly  from  $1.22  in  1900  to  $1.50  in  1912;. the  wages  of 
section  foremen  are  quite  uniformly  about  30  per  cent  above  those 
of  trackmen.  The  number  of  trackmen  per  100  miles  of  Hne  has 
also  increased  from  118  to  143  in  this  same  period,  but  there  have 


227 


216  RAILROAD  ENGINEERING 

been  greater  fluctuations.  The  increased  number  and  increased 
wages  have  combined  to  increase  very  greatly  the  cost  of  track 
maintenance. 

169.  Maintenance  of  Equipment.  The  cost  of  this  group  of 
items  has  been, increasing  very  greatly  in  recent  years,  not  only  in 
gross  amount  but  also  in  percentage  to  total  cost  of  a  train-mile 
and  in  cents  per  train-mile.  This  increased  cost  is  due  to  higher 
labor  costs  in  the  shops  and  higher  costs  for  materials.  While  a 
change  of  alinement,  involving  increase  or  decrease  in  length  of 
road,  or  ^'distance",  will  affect  these  items,  the  cost  is  not  directly 
proportional  to  distance  and  the  same  remark  applies  to  many  other 
items.  Curvature  afl'ects  the  cost  of  repairing  very  greatly — 
chiefly  in  wheel  wear,  and  the  engineer  must  consider  this  in  estimat- 
ing the  value  of  a  saving  in  curvature.  The  rate  of  grade  also  has 
an  effect  on  this  item. 

During  the  first  years  of  the  life  of  a  locomotive,  the  repairs 
(barring  accidents)  will  be  small,  but  as  the  locomotive  grows  older 
they  increase  in  a  growing  ratio.  When  the  annual  repair  charge 
becomes  one-fourth  (or  in  exceptional  cases  one-third)  of  its  first 
cost,%the  locomotive  should  be  sent  to  the  scrap  pile,  for  in  such 
eases  the  cost  per  train-mile  becomes  larger  than  a  reasonable  annual 
charge,  allowing  for  all  depreciation,  on  the  cost  of  a  new  locomotive. 
When  an  old  locomotive  is  replaced  by  one  of  a  better  and  more 
costly  type,  the  excess  cost  should  be  charged  to  '' betterments' ^ 
or  ''permanent  additions  to  equipment". 

170.  Transportation  Expenses.  There  are  five  items  in  this 
group  which  amount  to  more  than  5  cents  per  train-mile.  The 
largest  is  that  for  fuel.  The  cost  of  this  (for  both  yard  and  road 
locomotives)  has  nearly  doubled  since  1895.  This  is  due  partly  to 
increase  in  cost  of  coal  per  ton  and  partly  to  the  great  increase  in 
the  power  of  the  average  locomotive  and  therefore  in  the  amount  of 
coal  burned  per  mile.  The  other  four  of  the  five  large  items  are  made 
up  almost  exclusively  of  wages,  which  have  increased  very  greatly  in 
the  past  twenty  years.  Any  economic  calculation,  which  requires 
a  prediction  of  the  future  cost  of  operation,  must  include  the  proba- 
bility that  the  cost  of  conducting  transportation  will  probably  not 
decrease  and  may  increase  very  materially  even  during  the  next 
five  or  ten  years. 


228 


RAILROAD  ENGINEERING  217 

ECONOMIC  LOCATION 

171.  General  Principles  Involved.  A  hasty  mental  review  of 
the  previous  discussion,  as  well  as  a  few  considerations  of  common 
sense,  v^iW  show  the  truth  of  the  following  statements : 

(1)  Disregarding  the  comparatively  rare  cases  in  this  country 
where  a  practicable  location  of  any  kind  is  a  creditable  engineering 
feat,  it  may  be  said  that  a  comparatively  low  order  of  engineering 
talent  will  suffice  to  lay  out  a  line  along  any  general  route  over  which 
it  is  physically  possible  to  run  trains,  and  that  there  are  usually 
several  such  possible^routes.  The  route  selected  may  not  be  favor- 
ably located  for  obtaining  business,  its  alinement  may  be  such  that 
its  operating  expenses  are  high,  and  the  ruling  grades  may  be  so 
high  that  only  light  trains  can  be  run,  but  the  road  can  be  operated 
even  with  these  handicaps. 

(2)  Among  the  many  possible  routes  which  may  be  selected 
for  a  road,  there  is  one  which  is  superior  to  any  other  from  an  operat- 
ing or  business  standpoint,  and  it  is  the  province  and  test  of  the 
engineer  to  select  that  best  route. 

(3)  There  are  several  more  or  less  conflicting  interests  which 
must  be  studied — (a)  the  maximum  of  business  must  be  obtained, 
but  this  is  sometimes  only  obtainable  at  great  initial  cost;  (b)  the 
ruling  grades  must  be  made  as  low  as  possible,  which  is  generally 
costly,  and  it  inay  require  a  location  which  will  sacrifice  some  busi- 
ness; (c)  the  alinement  must  be  kept  easy  so  as  to  reduce  operating 
expenses,  but  this  usually  is  very  costly;  (d)  the  total  cost  must  be 
kept  within  a  figure  which  will  be  justified  by  the  future  earnings 
and  also  leave  enough  margin  as  working  capital  out  of  the  total 
funds  which  are  raised,  so  that  the  road  may  continue  to  operate 
during  the  five  or  ten  years  which  are  required  to  build  up  the 
^'normal"  traffic. 

(4)  Each  new  route  suggested  forms  a  new  combination  of 
the  above  conflicting  elements,  and  the  business  of  the  engineer  is 
to  estimate  and  compare  these  elements,  selecting  the  combination 
which  will  give  the  largest  return  for  the  least  outlay,  considering 
both  initial  cost  and  future  operating  expenses  as  elements  of  the 
outlay. 

172.  Reliability  and  Value  of  Economic  Calculations.  The 
student  should  not  form  the  idea  that  the  following  calculations 

229 


218  RAILROAD  ENGINEERING 

will  enable  one  to  compute  with  mathematical  precision  the  effect  of 
changes  of  alinement.  There  are  far  too  many  elements  involved, 
and  the  effect  of  certain  influences  is  variable.  But  although  a 
precise  solution  is  unobtainable,  a  solution  which  is  sufficiently 
accurate  for  practical  purposes  may  be  made,  and  this  is  infinitely 
better  than  no  solution  at  all.  For  example,  suppose  that  a  very 
crooked  stretch  of  road  may  be  changed  to  comparatively  easy 
alinement  which  saves  considerable  curvature  by  an  additional 
expenditure  of  say  $20,000.  Assume  that  it  has  been  computed  (by 
methods  developed  later)  that  the  operating  expenses  would  be 
reduced  $3500  per  year  by  the  reduction  of  that  curvature.  As  $3500 
per  year,  capitalized  at  5  per  cent,  is  equivalent  to  an  investment 
of  $70,000,  and  as  the  improvement  may  be  made  for  $20,000, 
the  improvement  is  evidently  justifiable.  Such  is  the  bare  outline 
of  the  method. 

The  estimate  of  the  cost  of  the  improvement  may  be  accurately 
made,  but  it  is  not  claimed  that  the  estimate  of  the  saving  per 
year  is  precise.  It  may,  however,  be  shown  that,  even  with  ample 
allowances  for  the  uncertain  items,  it  is  practicable  to  assign  upper 
and  lower  limits  between  which  the  truth  must  lie.  A  greater 
knowledge  of  the  subject  and  greater  experience  on  the  part  of  the 
engineer  will  enable  him  to  narrow  those  limits  so  that  the  error 
is  immaterial.  And  frequently  even  this  is  unnecessary.  The 
real  question  is  not  whether  the  capitaHzed  value  of  the  improve- 
ment is  $70,000,  or  $50,000,  or  $90,000.  It  may  be  that  an  improve- 
ment which  would  make  possible  that  saving  may  be  made  for  a 
few  thousand  dollars,  or  it  might  require  $200,000.  In  either  case, 
the  true  answer  is  unquestionable. 

If  the  cost  of  the  improvement  is  very  nearly  equal  to  its 
computed  capitalized  value,  then  no  great  harm  can  come  from 
either  decision,  for  the  decision  would  then  be  based  on  the  willing- 
ness of  the  company  to  spend  additional  money.  The  method 
furnishes  a  criterion,  which  even  in  the  hands  of  an  inexperienced 
engineer  has  some  value,  and  which  alone  gives  value  to  his  opinion. 
But  the  method  enables  the  experienced  engineer  to  give  the  best 
opinion  which  is  obtainable,  for  it  enables  him  to  apply  his  experience 
to  a  method  of  computation  which  approaches  accuracy  as  nearly 
as  may  be. 

230 


RAILROAD  ENGINEERING  219 

It  must  not  be  supposed  that  the  numerical  values  worked  out 
in  the  following  pages  are  necessarily  applicable  to  any  assumed 
case.  They  are  gi\'en  to  show  the  method  of  their  derivation,  and 
should  be  modified  to  fit  local  conditions  according  to  the  best 
judgment  of  the  engineer. 

DISTANCE 

173.  Relation  of  Distance  to  Rates  and  Expenses.  Rates 
are  usually  based  on  distance  traveled  on  the  apparent  assumption 
that  the  value  of  the  service  rendered  and  the  cost  to  the  company 
are  directly  proportional  to  the  number  of  miles  traveled.  The 
assumption  in  either  connection  is  not  true.  If  a  passenger  or 
a  load  of  freight  is  to  be  transported  from  one  city  to  another  city 
100  miles  away,  the  service  rendered  is  to  accomplish  the  transfer 
as  easily  and  quickly  as  possible.  If  another  road  were  constructed, 
perhaps  at  extravagant  cost,  by  which  the  distance  were  cut  dowTi 
to  90  miles,  that  road  would  render  a  greater  and  better  service, 
because  it  would  reduce  the  necessary  travel,  and  yet  on  the  mileage 
basis  the  shorter  road  would  be  entitled  to  less  than  the  other  in 
spite  of  the  fact  that  it  renders  a  better  service. 

The  assumption  that  the  cost  is  proportional  to  the  distance  is 
more  nearly  correct,  although,  as  will  be  shown  later,  even  this  is 
far  from  accurate.  It  is  not  difficult  to  compute  an  average  cost 
for  a  large  number  of  passenger  trains  and,  by  dividing  it  by  the 
total  passenger  mileage,  to  obtain  a  value  of  the  cost  of  a  "passenger- 
mile".  But  the  additional  cost  of  transporting  one  additional 
passenger  on  a  i«egular  train  is  hardly  more  than  the  cost  of  print- 
ing his  ticket.  Even  if  it  were  practicable  to  compute  the  extra 
consumption  of  coal  and  the  infinitesimal  addition  to  other  oper- 
ating expenses  due  to  his  being  on  the  train,  the  added  cost  would 
evidently  be  but  an  insignificant  fraction  of  the  average  cost  of  a 
passenger-train-mile.  The  same  argument  holds,  but  not  to  the 
same  extent,  if  we  consider  the  additional  cost  of  an  extra  ton  of 
freight. 

By  the  same  line  of  argument  it  will  be  shown  that  a  change 
in  distance  will  not  affect  the  cost  of  running  trains  in  proportion 
to  the  change.  It  is  easy  to  see  that  general  expenses  will  be  abso- 
lutely unaffected  by  an  alteration  of  alinement  which  saves  a  mile 

231 


220  RAILROAD  ENGINEERING 

in  distance,  and  it  will  be  shown  that  even  the  consumption  of  fuel 
does  not  vary  in  i)roportion  to  the  distance.  If  it  were  practicable 
to  construct  a  tariff  of  rates  which  should  consider  excessive  curva- 
ture and  grades  on  the  various  parts  of  the  line  and  make  the  rates 
dependent  on  them  as  well  as  on  many  other  constructive  features 
which  add  to  the  cost  of  operation,  the  rates  would  be  more  nearly 
proportional  to  the  cost,  but  the  public  would  not  appreciate  it  and 
it  would  be  useless  work.  And  when  it  is  further  shown  that  it  is 
sometimes  justifiable  for  a  road  to  haul  competitive  business  at  a 
rate  actually  less  than  the  average  cost  of  their  traffic,  it  will  be 
seen  that  the  relation  of  distance  to  rates  and  expenses  cannot  be 
expressed  by  any  simple  proportion. 

174.  Effect  on  Receipts.  Among  all  the  details  of  alinement, 
distance  is  the  one  for  which  there  is  some  compensation  in  an 
increase,  and  that  is  because  rates  are  based  on  distance  rather 
than  on  curvature  or  grades.  Although  it  is  unquestionably  con- 
trary to  public  policy  to  burden  traffic  unnecessarily  by  an  increase 
in  distance,  yet  it  may  be  demonstrated  that  the  added  receipts  from 
non-competitive  traffic  due  to  such  increased  distance  will  amount 
to  more  than  their  added  cost.  But  in  order  to  study  this  feature 
properly  the  distinction  between  competitive  and  non-competitive 
rates  must  be  noted.  For  our  purposes  traffic  may  be  classified  as 
"through"  and  as  *iocal",  in  which  through  traffic  refers  to  that 
which  passes  over  tivo  or  more  roads,  no  matter  how  long  or  short 
any  section  of  the  trip  may  be,  and  in  which  local  traffic  refers  to 
that  which  is  confined  to  one  railroad  system,  though  it  may  run 
from  one  end  to  the  other.  Further  subdivision  is  necessary  as 
follows : 

(1)  Non-competitive  local — on  one  road  with  no  choice  of 
routes. 

(2)  Non-competitive  through— on  two  (or  more)  roads  but 
with  no  choice. 

(3)  Competitive  local — a  choice  of  two  or  more  routes,  but 
the  entire  run  may  be  made  on  the  home  road. 

(4)  Competitive  through — direct  competition  between  two  or 
more  routes,  each  passing  over  two  or  more  lines. 

(5)  Semi-competitive  through — a  lion-competitive  haul  on  the 
home  road  and  a  competitive  haul  on  foreign  roads. 

232 


RAILROAD  ENGINEERING  221 

Receipts  for  traffic  passing  over  two  or  more  lines  are  divided 
between  the  lines  in  proportion  to  mileage.  "Terminal  charges" 
are  sometimes  subtracted  from  the  amount  before  the  division  is 
made  and  sometimes  a  strong  road  forces  a  weaker  road  to  submit 
to  some  other  exaction  before  the  division  is  made,  but  the  final 
,  division  is  made  in  proportion  to  the  mileage  for  each  passenger 
ticket  or  each  freight  bill.  It  may  be  shown  that  the  cost  of  oper- 
ating an  additional  mile  is  about  58  per  cent  of^the  average  cost. 
This  means  that  on  all  non-competitive  business  (class  1)  there 
is  an  actual  profit  in  this  added  distance.  On  the  other  hand,  com- 
petitive rates  are  made  with  small  regard  to  distance,  are  generally 
equal,  and  therefore  any  added  distance  results  in  a  sheer  loss  with- 
out any  compensation.    This  applies  to  all  the  traffic  of  class  3. 

Illustrative  Example.  The  other  classes  of  traffic  are  affected  by 
distance  in  various  degrees  between  these  two  extremes.  Suppose  that 
the  distance  on  the  home  road  for  any  given  shipment  is  100  miles, 
and  the  distance  on  the  foreign  road  for  that  shipment  is  150  miles; 
suppose  that  the  freight  charge  is  $10;  then  the  home  road  will 

receive X  $10  =  $4.00.     This  means   4  cents   per  mile  for 

100+150 

that  particular  class   and   weight   of  freight.     Suppose   that   the 

distance  is  increased  5  miles  on  the  home  road,  but  assume  that 

the  traffic  is  wholly  competitive  and  therefore  that  the  total  rate 

received  will  be  $10,  regardless  of  the  added  distance.    Then  the 

home  road  will  receive  ——^X$10  =  $4.1176.     If  we  allow  to 

lOo+loO 

the  original  100  miles  its  full  previous  allowance  of  4  cents  per 

mile,  we  have  left  11.76  cents  to  pay  for  the  extra  5  miles.     This 

is  at  the  rate  of  2.352  cents  per  mile,  which  is  58.8  per  cent  of  the 

4-cent  rate. 

This  nearly  equals  the  computed  percentage  of  added  cost 

for  additional  distance  computed  in  miles.     Therefore,  if  the  original 

4-cent  rate  is  profitable,  the  added  receipts  due  to  the  added 

distance  will  be  sufficient  to  operate  the  added  distance  profitably, 

or  without  loss.     Incidentally,  the  foreign  road  suffers,  for  it  will 

receive  less  for  precisely  the  same  service.    The  above  numerical 

case  is  very  nearly  at  the  dividing  line  between  profitable  and 

unprofitable  additition  to  distance.     If  the  length  of  the  home  road 

233 


222  RAILROAD  ENGINEERING 

is  but  a  small  proportion  of  the  total  distance,  then  it  may  be  simi- 
larly computed  that  an  addition  to  distance  is  distinctly  profitable. 
On  the  other  hand,  if  the  length  of  the  home  road  is  a  large  pro- 
portion of  the  total  distance,  an  addition  to  distance  is  distinctly 
unprofitable,  and  when  the  length  of  the  foreign  road  is  zero  (which 
means  that  the  competitive  haul  is  entirely  on  the  home  road)  then 
any  addition  to  distance  is  sheer  loss  without  any  compensation, 
even  partial. 

The  above  numerical  case  represents  but  one  of  an  almost 
infinite  number.  Each  station  along  the  line  has  possible  traffic 
connection  with  almost  every  other  railroad  station  in  the  country. 
The  route  from  each  station  to  every  other  station  represents  a  new 
combination,  and  the  net  effect  of  the  added  distance  is  the  com- 
bined effect  of  all  the  separate  cases.  This  instantly  shows  that  a 
precise  mathematical  solution  is  impossible,  but  the  above  solution 
has  value  in  pointing  out  some  general  truths  as  follows : 

In  all  non-competitive  business,  whether  through  or  local, 
the  added  receipts  due  to  added  distance  will  be  profitable,  and  if 
the  business  of  a  road  is  almost  entirely  non-competitive  there  is 
little  or  no  disadvantage  in  added  distance,  especially  if  the  construc- 
tion is  cheapened  in  spite  of  the  added  distance.  For  example, 
a  road  which  follows  the  banks  of  a  very  crooked  river  may  cost 
less  to  build,  even  though  much  longer  and  more  crooked,  than  the 
road  which  tunnels  through  the  horseshoe  bends. 

When  roads  handle  a  very  large  amount  of  competitive  busi- 
ness any  additional  distance  may  be  a  source  of  loss  on  that  class 
of  business,  and  the  loss  may  be  so  serious  as  to  justify  a  considerable 
expenditure  to  reduce  it.  Another  reason  for  the  subsequent 
expenditure  of  money  to  reduce  distance  is  that,  after  freight  rates 
are  once  established  between  roads  on  through  business,  they  are 
not  apt  to  be  disturbed  to  make  them  conform  to  the  slight  fluc- 
tuations of  distance  caused  by  changes  in  the  alinement. 

The  above  statements  can  be  reduced  to  the  general  conclusion 
that  since  every  road  handles  a  considerable  proportion  of  non- 
competitive business,  there  is  always  some  compensation  for  the 
added  expenses  of  operating  additional  distance.  The  majority  of 
small  roads  do  a  business  which  is  almost  wholly  non-competitive, 
and  to  them  the  added  receipts  will  usually  pay  for  the  added  dis- 

234 


RAILROAD  ENGINEERING  223 

tance,  even  if  it  is  not  an  actual  source  of  profit.  Finally,  it  may 
be  said  that  a  road  is  not  usually  justified  in  making  an  additional 
expenditure  to  shorten  distance  (i.e.,  adopt  a  route  which  will  have 
a  greater  gross  cost  in  spite  of  the  shortened  distance)  unless  it 
handles  a  very  large  amount  of  highly  competitive  business. 

There  are  some  other  considerations  which  must  not  be  ignored 
in  considering  this  question.  One  of  them  is  the  question  of  the 
additional  time  required  to  make  the  trip.  This  may  be  important 
in  two  ways.  (1)  The  competition  for  passenger  business  between 
two  cities,  such  as  New  York  and  Philadelphia,  or  Philadelphia 
and  Atlantic  City,  might  be  so  keen  that  a  difference  in  length 
of  line  which  would  affect  the  running  time  by  even  10  minutes 
would  have  great  financial  importance.  (2)  A  very  considerable 
change  in  distance  may  have  a  serious  effect  on  the  operation  of 
the  heavy  through-freight  trains,  although  it  would  not  ordinarily 
increase  the  total  cost  of  operating  those  trains  over  that  division 
more  than  the  extra  number  of  train-miles  times  the  reduced  train- 
mile  cost.  But  in  any  case,  this  phase  of  the  question  should  not 
be  ignored. 

Another  consideration  is  the  possible  effect  on  the  business 
done.  "A  short  straight  line"  is  the  popular  description  of  a  well- 
designed  road.  If  the  engineer's  aim  for  a  short  road  leads  him  to  pass 
by  sources  of  income  and  thus  lose  them,  his  road  will  have  little 
business  and  the  receipts  will  be  reduced  because  it  is  short.  As  a  gen- 
eral rule  ''adopt  that  route  which  will  give  the  greatest  traffic  per  mile 
of  road".  On  the  one  hand,  this  avoids  the  error  of  running  a  line 
which  is  excessively  crooked  in  the  effort  to  secure  every  possible 
element  of  traffic  and  thus  burdening  the  whole  traffic  with  an 
excessive  haul,  and  on  the  other  hand,  avoids  running  a  line  which 
misses  important  sources  of  traffic  in  the  effort  to  have  a  straight 
fine. 

CURVATURE 

175.  Operating  Disadvantages  of  Curvature.  The  non-tech- 
nical mind  appreciates,  even  too  readily,  the  disadvantages  of 
curvature.  But  it  is  generally  true  that  the  ones  which  are  most 
thoroughly  appreciated  by  the  pubfic  are  of  least  economic  value 
to   the   engineer.     The   several   disadvantages   ^\^ll    be    classified 


224  RAILROAD  ENGINEERING 

and  discussed  in  an  order  which  is  perhaps  the  inverse  order  of 
their  importance,  as  follows: 

(1)  It  increases  the  danger  of  collision  and  derailment  and 
aggravates  the  damages  of  a  derailment  when  it  occurs.  The  appli- 
cation to  be  made  to  this  statement  of  undoubted  fact  is — how 
much  is  a  road  justified  in  expending  in  order  to  reduce  or  elimi- 
nate any  given  curve?  Since  the  entire  elimination  of  curves  is  a 
physical  as  well  as  a  financial  impossibility,  the  question  reduces 
to  the  lessening  of  danger  from  accidents  that  would  result  from 
such  reductions  as  are  possible.  The  Interstate  Commerce  Com- 
mission report  on  railroad  accidents  for  the  year  ending  June  30, 
1902,  showed  that  the  number  of  passengers  carried  1  mile  for  one 
killed  was  57,022,283.  This  means  that  the  chances  are  even  that 
a  passenger  could  ride  57,000,000  miles  before  he  would  be  killed. 
If  he  were  to  ride  continuously  at  the  rate  of  60  miles  per  hour,  it 
would  require  over  9,500,000  hours,  or  nearly  400,000  days,  which  is 
considerably  over  1000  years. 

But  how  many  of  such  casualties  are  due  to  curvature,  and 
how  many  million  miles  must  be  traveled  by  the  average  passenger 
before,  according  to  the  law  of  probabilities,  he  would  be  killed 
by  an  accident  which  should  not  only  be  directly  charged  to  cur- 
vature, but  also  to  curvature  w^hich  is  physically  or  financially 
avoidable.  If  we  estimate  the  number  of  curves  on  all  the  railroads 
of  the  country  as  250,000,  what  is  the  probability  of  a  fatal  accident 
happening  on  any  one  curve  and  how  much  may  be  spent  on  that 
curve  to  reduce  the  danger?  Even  if  it  were  spent,  would  there 
remain  no  danger  of  an  accident  there?  A  thorough  logical  analysis  of 
this  question  shows  that  although  it  is  always  proper  to  take  reason- 
able precautions  to  avoid  accident  at  an  especially  dangerous 
curve  (such  as  maintaining  a  flagman  there),  it  is  impossible  to 
assign  any  financial  value  to  the  mere  danger  of  accident  which 
would  accomplish  anything  toward  modifying  construction. 

(2)  Curvature  may  affect  traffic  (a)  by  reducing  the  possible 
speed  of  fast  trains.  There  is  some  force  to  this  objection  as  it 
applies  to  sharply  competitive  traffic  between  two  cities — a  traffic 
of  which  most  roads  have  not  a  trace.  The  extent  to  which  the 
passenger  traffic  might  be  increased  by  the  minute  or  two  which 
might   be  saved  is,  however,  so  uncertain  that  it  defies  analysis. 

236 


RAILROAD  ENGINEERING  225 

(b)  It  may  produce  rough  riding,  and  (c)  it  may  create  an  apprehen- 
sion of  danger  which  may  of  itself  deter  travel.  The  disadvantages 
resulting  from  all  three  of  these  sub-causes  are  greatly  reduced  by 
good  roadbeds  and  transition  curves.  Freight  traffic,  which  com- 
prises about  two-thirds  of  the  total,  is  unaffected  by  it  unless  the 
curvature  is  extreme,  and  the  passenger  traffic  of  most  roads  will 
not  be  influenced  by  it;  and  therefore  an  engineer  is  not  ordinarily 
justified  in  giving  it  any  financial  weight. 

(3)  It  may  affect  the  operation  of  trains  (a)  by  limiting  their 
length  and  (b)  by  limiting  the  type  and  weight  of  engines.  There 
are  a  few  instances  known  where  roads  which  run  along  a  river 
bank  have  very  easy  ruling  grades  and  on  which  the  curvature  is 
perhaps  very  sharp  on  account  of  sharp  bends  in  the  river.  On 
such  roads  the  curvature  may  be  the  feature  which  limits  the  length 
of  trains,  but  such  cases  are  rare  and  even  when  they  occur  a  com- 
putation similar  to  that  later  developed  will  show  how  much  may 
profitably  be  spent  to  reduce  the  rate  of  curvature.  If  a  long  grade 
up  a  mountain  were  kept  uniform,  regardless  of  curves,  the  curves 
would  add  such  resistance  that  they  would  limit  the  length  of  trains, 
but  good  practice  requires  that  the  grades  shall  be  "compensated 
for  curvature",  as  explained  later. 

The  excessively  sharp  curvature  which  has  been  used  on  some 
mountain  roads  may  preclude  the  use  of  some  of  the  largest  types 
of  locomotives.  But  such  roads  ordinarily  do  not  have  a  traflSc 
which  justifies  the  use  of  the  heaviest  locomotives.  And  when  it 
is  considered  that  a  Mallet  locomotive,  having  sixteen  drivers 
and  a  weight  on  the  drivers  of  over  400,000  pounds,  can  be  operated 
on  a  20-degree  curve,  any  limitation  in  the  use  of  engines  may  be 
ignored  for  all  ordinary  railroad  work. 

(4)  Curvature  increases  operating  expenses.  This  disadvan- 
tage is  definite,  positive,  and  approximately  computable,  and  since 
a  reduction  in  expenses  may  be  made  by  reducing  curvature,  we 
must  calculate  the  effect  of  curvature  on  operating  expenses. 

.  176.  Compensation  for  Curvature.  Curvature  makes  a  very 
definite  increase  in  train  resistance,  and  such  increased  resistance 
is  readily  equated  to  its  equivalent  in  added  grade.  Assuming 
that  the  curve  resistance  on  a  6-degree  curve  is  4  pounds  per  ton, 
which  is  the  grade  resistance  of  a  0.2-per-cent  grade,  if  there  should  be 

237 


226  'RAILROAD  ENGINEERING 

a  6-degree  curve  on  a  1 .0-per-cent  grade,  the  resistance  on  that  grade 
would  be  the  same  as  on  a  straight  track  having  a  1.2-per-cent 
grade.  On  this  basis,  if  1.2  per  cent  were  selected  as  the  ruling 
grade  and  it  became  necessary  to  introduce  a  6-degree  curve,  the 
grade  should  be  reduced  on  that  curve  to  1  per  cent  so  that  the  total 
resistance  on  that  curve  shall  be  no  greater  than  on  the  tangent. 
This  is  the  fundamental  idea  of  curve  compensation.  On  grades 
which  are  so  low  that  they  will  never  be  ruling  grades  even  if  the 
rate  of  ruling  grade  is  reduced  by  reconstruction,  there  is  no  neces- 
sity for  curve  compensation,  but  the  neglect  of  it  on  ruling  grades 
means  that  the  ruling  grade  is  practically  increased  to  the  grade 
which  is  the  equivalent  of  the  combined  grade  and  curve  resistance. 
Rate  of  Compensation.  This  term  means  such  a  reduction  in  the 
grade  that  the  saving  in  grade  resistance  equals  the  curve  resistance. 
But  curve  resistance  varies  somew^hat  as  the  velocity,  the  condition 
of  the  rails,  and  even  the  type  of  the  wheel  base.  For  simplicity  of 
calculation  the  curve  resistance  is  usually  assumed  to  vary  as  the 
degree  of  curvature.  While  this  is  nearly  true  for  low  degrees  of 
curvature,  it  becomes  grossly  inaccurate  for  excessively  sharp  curva- 
ture, on  which  the  resistance  is  fortunately  much  less  than  its  pro- 
portionate amount.  This  is  probably  due  to  the  fact  that  a  large 
part  of  the  resistance  from  curvature  is  due  to  causes  which  are 
independent  of  the  degree  of  curve.  The  resistance  will  amount 
to  about  2  pounds  per  ton  per  degree  of  curve  (equivalent  to  a  0.1- 
per-cent  grade)  when  the  velocity  is  very  low — as  when  starting  a 
train.  It  is  less  for  fast  trains  than  for  slow  trains,  but  considering 
that  it  is  the  slow  and  heavy  freight  trains  w^hich  must  be  chiefly 
considered,  the  larger  values  for  compensation  which  are  needed 
for  the  slower  velocities  must  be  used.  Compensation  results  in 
a  loss  of  elevation  for  a  given  horizontal  distance  and  when  money 
has  been  spent  in  "development"  in  order  to  reduce  the  grade 
to  some  desired  limit,  any  useless  compensation  is  a  waste  and 
should  be  avoided.  If  a  curve  occurs  on  a  grade  immediately 
below  a  stopping  place  for  all  trains  (or  at  least  all  trains  which 
are  so  heavy  that  they  will  be  affected  by  the  ruling  grade),  the 
compensation  may  be  reduced  or  omitted  altogether  on  the  ground 
that  the  curve  resistance  would  simply  use  up  the  energy  which 
might  otherwise  be  used  up  by  brakes  in  stopping  the  train.    If 

238 


RAILROAD  ENGINEERING  227 

that  heavy  grade  should  continue  on  above  that  stopping  place, 
then  the  compensation  should  be  made  even  greater  than  the  aver- 
age to  allow  for  the  increased  resistance  while  starting.  Since 
the  curve  resistance  merely  adds  to  the  virtual  grade,  and  the 
object  of  compensation  is  to  prevent  such  additions  from  increasing 
the  ruling  grade,  there  is  no  object  in  using  compensation  on  a 
grade,  which  is  already  so  low  that  the  added  resistance  will  not 
make  it  virtually  equal  to  the  ruling  grade.  An  exception  to  this 
lies  in  the  danger  that  it  may  some  time  prove  desirable  to  make 
such  changes  of  alinement  that  the  ruling  grade  is  very  materially 
cut  down,  and  it  might  happen  that  neglect  to  compensate  would  add 
that  much  to  the  revised  ruling  grade.  The  above  discussion  may 
therefore  be  reduced  to  the  following  rules: 

(1)  On  the  upper  side  of  a  stopping  place  for  all  heavy  trains 
compensate  0.10  per  cent  per  degree  of  curve. 

(2)  On  the  lower  side  of  such  a  stopping  place  do  not  com- 
pensate at  all — but  this  rule  should  be  applied  cautiously. 

(3)  Ordinarily  compensate  about  0.035  per  cent  per  degree 
of  curve. 

(4)  Increase  this  rate  to  0.04  per  cent  when  the  curve  is  habit- 
ually operated  at  slow  speed,  or  when  the  super-elevation  is  excessive 
for  freight  trains,  unless  it  is  found  that  the  higher  rate  of  com- 
pensation causes  such  a  loss  of  height  that  the  grade  on  the  tangent 
must  be  increased. 

(5)  Curves  which  are  so  much  less  than  the  ruling  grade, 
that  they  will  always  be  minor  grades  need  not  be  compensated, 
but  the  possfbilities  of  a  future  reduction  in  the  rate  of  ruling  grade 
should  be  considered. 

177.  Limitations  of  Curvature.  Surveys  for  railroads  are 
frequently  made  under  instructions  that  curves  (and  also  grades) 
shall  not  exceed  some  chosen  limitations.  What  should  be  the 
limitation,  if  any,  of  the  degree  of  curvature?  Probably  no  definite 
answer  is  correct  unless  it  be  said  that  there  should  be  no  limita- 
tion. It  has  been  shown  that  all  ordinary  degrees  of  curvature  even 
up  to  20  degrees  will  still  permit  the  use  of  heavy  engines,  and  there  are 
numerous  instances  where  a  heavy  railroad  traffic  has  been  hauled 
for  many  years  around  excessively  sharp  curves  without  any  serious 
difficulty — as,  for  instance,  the  traffic  on  the  Baltimore  &  Ohio 

239 


228  RAILROAD  ENGINEERING 

Railroad  at  Harper's  Ferry,  which  for  many  years  was  hauled  around 
a  19-degree  10-minute  curve  (radius  300  feet).  This  curve  was 
changed  some  years  ago.  Of  course  the  young  engineer  should  not 
conclude  from  this  that  curvature  is  of  no  consequence,  and  that  he 
may  recklessly  put  in  as  much  and  as  sharp  curvature  as  might  seem 
at  first  the  easiest  plan  to  adopt.  It  may  be  shown  that  there  is  a 
definite  money  value  in  reducing  every  possible  degree  of  central  angle 
and  also  that  the  radius  of  curvature  should  be  made  as  large  as  pos- 
sible without  a  serious  sacrifice  of  other  interests  or  extravagant 
expenditure.  It  generally  happens,  when  running  a  road  through  a 
mountainous  country,  and  when  a  high  summit  must  be  crossed, 
that  the  grades  can  only  be  reduced  by  the  adoption  of  very  sharp 
curvature  or  by  a  large  expenditure  in  construction.  Since  the 
expenditure  is  usually  limited  by  financial  considerations,  the  error 
of  adopting  a  high  ruling  grade  is  usually  made  and  the  degree  of 
curvature  is  limited  to  a  low  figure  which  is  ridiculously  out  of 
proportion  to  the  general  condition  of  the  road. 

Sometimes  the  limited  money  at  the  disposal  of  the  company 
is  wasted  on  a  route  which  gives  easy  curves  when  the  money  could 
have  been  spent  advantageously  in  other  ways.  The  most  com- 
mon error  is  the  needless  increase  in  the  ruling  grade.  Many  rail- 
roads have  been  laid  out  under  the  instructions  that  the  maximum 
grade  may  be  60  feet  per  mile  and  the  minimum  curve  6  degrees.  These 
limits  have  been  used  separately,  or  in  combination,  with  the  result 
that  when  a  6-degree  curve  occurred  on  a  60-foot  grade,  the  virtual 
grade  was  thereby  increased  (on  a  0.035-per-cent  basis)  to  over  71  feet 
per  mile.  While  a  grade  of  60  feet  per  mile  might  be  la  very  proper 
ruling  grade  under  certain  conditions,  it  might  readily  happen  that 
the  option  of  using  a  lO-degr^e  curve  (properly  compensated)  would 
permit  adopting  a  line  with  a  ruling  grade  so  much  less  than  60 
feet  that  the  advantages  of  the  reduction  of  grade  would  far  out- 
weigh the  comparatively  insignificant  disadvantages  of  the  sharp 
curvature.  Therefore,  as  a  general  answer  it  may  be  said  that  the 
limits,  if  any,  should  conform  to  the  general  character  of  the  country, 
and  that  when  it  appears  possible  to  obtain  a  great  advantage, 
such  as  the  reduction  of  the  ruling  grade,  by  an  increase  in  the 
degree  of  curvature  and  even  in  the  degrees  of  central  angle,  such 
increase  should  be  made  unless  it  may  be  definitely  computed 

240 


RAILROAD  ENGINEERING  229 

that  the  disadvantages  of  the  increased  curvature  would  outweigh 
the  advantages  of  the  reduced  grade. 

GRADE 

178.     Distinction  between    Minor  and   Ruling  Grades.    The 

distinction  between  minor  and  ruUng  grades  must  be  very  clearly 
understood  before  their  operating  disadvantages  may  be  computed. 
The  cost  of  running  a  train  one  mile  is  largely  independent  of  whether 
the  train  is  long  or  short,  heavy  or  light.  The  receipts  for  transport- 
ing so  many  tons  of  freight  is  a  definite  quantity  and  is  unaffected 
whether  it  is  transported  in  one  train  load  or  two.  If  it  is  possible 
by  a  reduction  in  grade  to  haul  in  a  single  train  load  as  much  freight 
as  would  require  two  train  loads  by  the  old  plan,  then,  since  the 
receipts  are  constant  and  the  cost  of  the  two  light  trains  will  be 
nearly  double  that  of  the  one  heavy  train,  it  is  evident  that  the 
low-grade  plan  will  be  very  profitable  and  the  other  plan  corre- 
spondingly costly  and  financially  ruinous. 

Although  it  is  not  often  practicable  to  double  the  weight  of 
the  train  behind  a  freight  engine,  a  very  material  increase  in  the 
train  load  can  generally  be  made  by  such  reduction  of  the  ruling 
grade  as  is  practicable,  and  such  increase  in  train  load  frequently 
makes  all  the  difference  between  large  dividends  and  an  actual 
deficit.  The  ruling  grade  definitely  limits  the  load  that  can  be 
hauled  by  an  engine  with  a  given  weight  on  the  drivers  and  its 
financial  effect  is  very  great.  On  the  other  hand,  a  minor  grade 
does  not  limit  the  number  of  cars  and  its  effect  on  operating  expenses 
is  confined  chiefly  to  an  increase  in  the  consumption  of  fuel  and 
other  locomotive  supplies.  While  this  increase  in  expense  has  an 
importance  which  is  worth  computing,  it  is  insignificant  compared 
with  the  cost  of  running  additional  trains  to  handle  a  given  traffic. 

The  real  cost  of  minor  grades  is  also  less  than  it  might  other- 
wise be  considered  owing  to  the  fact  that  each  rise  has  its  corre- 
sponding fall.  Even  though  several  high  summits  may  be  crossed, 
the  difference  in  elevation  of  the  terminals,  say  200  feet,  or  even  500 
feet,  is  insignificant  from  the  standpoint  of  grade  when  the  distance 
is  perhaps  as  many  miles.  And  even  in  the  extreme  case  when 
the  grade  is  all  in  one  direction,  the  additional  energy  required 
to  climb  the  grades  is  partly  returned  in  the  assistance  the  grade 

241 


230  RAILROAD  ENGINEERING 

gives  to  trains  on  the  return  trip  and  the  consequent  saving  in 
motive  power. 

179.  Laws  of  Accelerated  Motion.  Application  to  Movement 
of  Trains.  When  a  train  starts  from  rest  and  acquires  its  normal 
velocity,  say  30  miles  per  hour,  the  engine  must  develop  not  only 
the  power  required  for  all  the  ordinary  tangent  and  perhaps  curve 
and  grade  resistances,  but  also  the  "kinetic  energy"  corresponding 
to  the  velocity  which  has  been  acquired.  This  kinetic  energy 
is  not  wasted;  all  of  it  is  transformed  back  into  work  of  some  kind. 
The  energy  may  be  consumed  and  wasted  in  the  brakes,  but  it 
may  also  be  spent  (and  is  so  spent)  in  overcoming  resistances  when- 
ever the  velocity  of  the  train  is  reduced.  The  amount  of  this 
kinetic  energy  is  a  definite  mathematical  quantity.  The  laws  of 
Mechanics  tell  us  that  this  energy  equals  W  (v'^-T-2g),  in  which  W  is 
the  weight  of  the  train,  v  is  its  velocity  in  feet  per  second,  and  g  is 
the  acceleration  of  the  force  of  gravity,  which  equals  32.16  feet 
per  second  in  a  second. 

A  better  appreciation  of  this  force  may  be  obtained  by  con- 
sidering for  a  moment  that  if  the  train  could  move  along  the  track 
without  any  resistance,  then,  when  running  at  a  velocity  of  v  feet 
per  second,  it  possesses  a  kinetic  energy  which  would  raise  it  to  a 
height  of  h  feet,  where  h  =  v^-i-2g.  If  we  consider  that  the  engine 
is  furnishing  exactly  the  power  required  to  overcome  the  tractive 
resistances,  then  the  train  would  run  until  it  had  climbed  a  grade 
to  a  height  of  h  feet,  no  matter  whether  it  was  accomplished  in 
100  feet,  or  a  mile.  By  an  expansion  of  the  theory  it  is  also  shown 
that  when  the  train  has  climbed  a  vertical  height  of  h^  feet  (less 
than  h)j  it  will  have  left  a  velocity  v'  =y2g  {h  —  W). 

Illmtrative  Example.    Assume  that  the  velocity  of  a  train  is  30 

miles  per  hour,  or  44  feet  per  second.     It  then  has  a  kinetic  energy 

442 
which    would    raise    it    a    height    h  =  - — ^1777.  =  '^^^-1   ^^'^t.     If  the 

engine  furnished  just  enough  energy  to  overcome  the  tractive 
resistances,  the  kinetic  energy  would  carry  the  train  up  a  grade 
of  15  feet  per  mile  for  a  distance  of  about  2  miles,  or  up  a  grade  of 
60  feet  per  mile  for  a  distance  of  about  |  mile.  If  the  train  were 
moving  up  a  grade  of  20  feet  per  mile  and  had  proceeded  half  a 
mile,  it  would  have  climbed  10  feet  and  would  still  have  a  kinetic 

242 


RAILROAD  ENGINEERING  231 

energy  corresponding  to  20.1  feet,  and  its  velocity  would  then  be 
/  =  V2X32.16X20.1=35.9  feet  per  second,  or  24.5  miles  per  hour. 

If  the  train  were  a  solid  mass  the  above  figures  would  be  abso- 
lutely correct,  but  the  solution  is  a  little  complicated  by  the  fact 
that  an  appreciable  part  of  the  weight  of  the  train  consists  of 
revolving  wheels,  to  w^hich  must  be  imparted  the  kinetic  energy 
of  rotation,  in  addition  to  the  kinetic  energy  of  translation.  The 
ratio  of  this  rotative  kinetic  energy  to  that  of  translation  depends 
chiefly  on  the  ratio  of  the  weights  of  the  wheels  and  of  the  whole 
car  or  engine.  Evidently  this  ratio  depends  on  the  detailed  design 
of  the  rolling  stock,  and  more  especially  on  whether  the  cars  are 
loaded  or  empty.  This  consideration  shows  that  no  one  value  will 
be  accurate  for  all  cases,  but  there  will  be  little  error  in  adopting 
5  per  cent  as  an  average  value  for  the  increase  in  the  kinetic  energy. 

Table  XVII,  which  will  be  found  very  useful  in  these  com- 
putations, has  therefore  been  compiled  on  the  following  basis: 

.t^j  1     .^    ,       i„    ^^  in  ft.  per  sec.     1.4667  V^  in  m.  per  h. 
Velocity  head   =-^-^^^^= ^4.32 

=  0.03344  F2 
and,  adding  5  per  cent  for  rotative 
kinetic  energy  of  the  wheels,  =  0.00167  F^ 

Therefore,  corrected  velocity  head  =  0.0351  IF^ 

Part  of  the  figures  of  Table  XVII  were  obtained  by  interpola- 
tion, and,  therefore,  there  may  be  an  error  of  a  single  unit  in  the  hun- 
dredths place  in  some  of  the  figures,  but  considering  the  uncertainties 
in  the  problem,  the  exact  value  to  hundredths  is  of  no  prac- 
tical importance.  Examples  of  the  application  of  this  table  will  be 
given  later. 

The  tractive  force  required  to  produce  this  acceleration  in 
a  given  distance  may  be  stated  as 

W 
2gs 
in  which  Vi  and  Vz  are  the  lower  and  higher  velocities  in  feet  per 
second,  s  is  the  distance  in  feet,  g  is  the  acceleration  of  gravity 
(32.16),  and  W  is  the  weight  in  pounds.     If  we  substitute  1^  =  2000 

(or  one  ton),  gf  =  32.16,  Vi=  Vi  — — ,  and2?2=  V2  7——,  to  reduce  the 

3600  3600 


243 


TABLE  XVII 

Velocity  Head  (Proportional  to  Kinetic  Energy)  of  Trains 
Moving  at  Various  Velocities 


Velocity 

Velocity  Head 

(miles  per 

F2X0. 03511 

hour) 

0.0   ■ 

0.1 

0.2 

0.3 

0.4 

0.5 

0.6 

0.7 

0.8 

0.9 

5 

0.88 

0.91 

0.95 

0.99 

1.02 

1.06 

1.10 

1.14 

1.18 

1.22 

6 

1.26 

1.31 

1.35 

1.40 

1.44 

1.48 

1.53 

1.58 

1.62 

1.67 

7 

1.72 

1.77 

1.82 

1.87 

1.92 

1.97 

2.03 

2.08 

2.14 

2.19 

8 

2.25 

2.30 

2.36 

2.42 

2.48 

2.54 

2.60 

2.66 

2.72 

2.78 

9 

2.85 

2.91 

2.97 

3.04 

3.10 

3.17 

3.24 

3.30 

3.37 

3.44 

10 

3.51 

3.58 

3.65 

3.72 

3.79 

3.87 

3.95 

4.02 

4.10 

4.17 

11 

4.25 

4.33 

4.41 

4.49 

4.57 

4.65 

4.73 

4.81 

4.89 

4.97 

12 

^5.06 

5.15 

5.23 

5.32 

5.41 

5.50 

5.58 

5.67 

5.75 

5.84 

13 

5.93 

6.02 

6.12 

6.21 

6.31 

6.40 

6.50 

6.59 

6.69 

6.78 

14 

6.88 

6.98 

7.08 

7.19 

7.29 

7.39 

7.49 

7.60 

7.70 

7.80 

15 

7.90 

8.00 

8.11 

8.22 

8.33 

8.44 

8.55 

8.66 

8.77 

8.88 

16 

8.99 

9.10 

9.21 

9.32 

9.43 

9.55 

9.67 

9.79 

9.91 

10.03 

17 

10.15 

10.27 

10.39 

10.51 

10.63 

10.75 

10.87 

10.99 

11.12 

11.25 

18 

11.38 

11.50 

11.63 

11.76 

11.89 

12.02 

12.15 

12.28 

12.41 

12.55 

19 

12.68 

12.81 

12.95 

13.08 

13.22 

13.35 

13.49 

13.63 

13.77 

13.91 

20 

14.05 

14.19 

14.33 

14.47 

14.61 

14.75 

14.89 

15.04 

15.19 

15.34 

21 

15.49 

15.64 

15.79 

15.94 

16.09 

16.24 

16.39 

16.54 

16.69 

16.84 

22 

17.00 

17.15 

17.30 

17.46 

17.62 

17.78 

17.94 

18.10 

18.26 

18.42 

23 

18.58 

18.74 

18.90 

19.06 

19.22 

19.38 

19.55 

19.72 

19.89 

20.06 

24 

20.23 

20.40 

20.57 

20.74 

20.91 

21.08 

21.25 

21.42 

21.59 

21.77 

25 

21.95 

22.12 

22.30 

22.48 

22.66 

22.84 

23.02 

23.20 

23.38 

23.56 

26 

23.74 

23.92 

24.10 

24.28 

24.46 

24.65 

24.84 

25.03 

25.22 

25.41 

27 

25.60 

25.79 

25.98 

26.17 

26.36 

26.55 

26.74 

26.93 

27.13 

27.33 

28 

27.53 

27.73 

27.93 

28.13 

28.33 

28.53 

28.73 

28.93 

29.13 

29.33 

29 

29.53 

29.73 

29.93 

30.13 

30.34 

30.55 

30.76 

30.97 

31.18 

31.39 

30 

31.60 

31.81 

32.02 

32.23 

32.44 

32.65 

32.86 

33.08 

33.30 

33.52 

31 

33.74 

33.96 

34.18 

34.40 

34.62 

34.84 

35.06 

35.28 

35.50 

35.72 

32 

35.95 

36.17 

36.39 

36.62 

36.85 

37.08 

37.31 

37.54 

37.77 

38.00 

33 

38.23 

38.46 

38.69 

38.92 

39.15 

39.38 

39.62 

39.86 

40.10 

40.34 

34 

40.58 

40.82 

41.06 

41.30 

41.54 

41.78 

42.02 

42.26 

42.51 

42.76 

35 

43.01 

43.26 

43.51 

43.76 

44.01 

44.26 

44.51 

44.76 

45.01 

45.26 

36 

45.51 

45.76 

46.01 

46.26 

46.52 

46.78 

47.04 

47.30 

47.56 

47.82 

37 

48.08 

48.34 

48.60 

48.86 

49.12 

49.38 

49.64 

49.91 

50.18 

50.45 

38 

50.72 

50.99 

51.26 

51.53 

51.80 

52.07 

52.34 

52.61 

52.88 

53.15 

39 

53.42 

53.69 

53.96 

54.23 

54.51 

54.79 

55.07 

55.35 

55.63 

55.91 

40 

56.19 

56.47 

56.75 

57.03 

57.31 

57.59 

57.87 

58.16 

58.45 

58.74 

41 

59.03 

59.32 

59.61 

59.90 

60.19 

60.48 

60.77 

61.06 

61.35 

61.64 

42 

61.94 

62.23 

62.52 

62.82 

63.12 

63.42 

63.72 

64.02 

64.32 

64.62 

43 

64.92 

65.22 

65.52 

65.82 

66.12 

66.43 

66.74 

67.05 

67.36 

67.67 

44 

67.98 

68.29 

68.60 

68.91 

69.22 

69.53 

69.84 

70.15 

70.46 

70.78 

244 


RAILROAD  ENGINEERING  233 

velocities  Vi  and  V2  (which  are  in  feet  per  second)  to  Vi  and  V2, 
the  velocities  in  miles  per  hour,  the  equation  becomes 

Adding  5  per  cent  for  the  kinetic  energy  of  rotation,  the  coefficient 
66.89  becomes  70.23,  but,  considering  that  the  5  per  cent  correction 
is  somewhat  approximate  and  variable,  the  coefficient  is  taken 
at  the  even  figure  of  70  and  the  equation  becomes 

70 

.  p  =  ^  (Fa^-Fi^)  (104) 

s 

in  which  P  is  the  force  in  pounds  per  ton  to  accelerate  a  train  from 
a  velocity  of  Vi  miles  per  hour  to  V2  miles  per  hour  in  a  distance 
of  s  feet.  Conversely,  P  is  the  force  in  pounds  per  ton  which  can 
be  utilized  in  overcoming  tractive  or  grade  resistance  when  the 
velocity  is  reduced  from  ]\  m.p.h.  to  W  m.p.h.  in  a  distance  of 
s  feet. 

180.  Virtual  Profile.  The  following  demonstrations  are  made 
on- the  basis  that  the  ordinary  tractive  resistances  and  also  the 
tractive  force  of  the  locomotive  are  independent  of  velocity.  Neither 
of  these  assumptions  is  strictly  true,  especially  the  latter.  The 
variation  of  tractive  power  with  velocity  will  be  considered  later 
(article  191).  But  the  approximate  results  obtained  on  the  basis 
of  these  two  assumptions  are  so  instructive  and  useful  that  the 
demonstration  is  given.  Assume  that  Fig.  157  shows  the  profile 
of  a  section  of  road  and  that  the  grade  of  ^  E  is  0.40  per  cent, 
which  is  21.12  feet  per  mile.  Assume  also  that  a  freight  engine 
which  is  climbing  up  the  grade  has  been  so  loaded  that  when  the 
engine  is  working  uniformly  at  its  normal  maximum  the  velocity 
up  such  a  grade  would  be  uniformly  20  miles  per  hour.  But  since 
the  train  is  moving  at  20  miles  per  hour  it  has  akinetic  energy 
corresponding  to  a  velocity  of  14.05  feet  (see  Table  XVII).  At  A  it 
encounters  a  downgrade  of  0.20  per  cent,  which  is  1500  feet  long. 
Although  A  B  has  a  dowTigrade  of  only  0.2  per  cent,  its  grade  with 
respect  to  the  upgrade  oi  A  E  (0.40  per  cent)  is  0.60  per  cent.  There- 
fore B  is  9.00  feet  below  B'.  Since  the  work  done  by  the  engine 
would  have  carried  the  train  up  to  the  point  5'  with  a  velocity 
of  20  miles  per  hour,  the  virtual  drop  of  9  feet  will  increase  the 


234 


RAILROAD  ENGINEERING 


50-I7I 


u 


s 


'^^\ 


\    (V 


^"p-b>7 


velocity  head  from  14.05  feet  to  23.05 
feet,  which  corresponds  to  the  velocity 
of  25.6  miles  per  hour,  and  this  will 
actually  be  the  velocity  of  the  train  at 
the  point  B.  At  B  the  grade  changes 
to  a  1 .0-per-cent  upgrade  for  a  distance 
of  2300  feet. 

The  approach  of  the  grade  B  C  to 
the  grade  B'  C  is  at  the  rate  of  1.0-0.4, 
or  0.6  per  cent  and  tlierefore  the  point  C 
will  be  reached  in  1500  feet.  In  the  re- 
maining 800  feet  the  line  will  cHmb  to  7), 
which  is  4.8  feet  above  D'.  Although 
at  B  the  train  is  moving  at  the  rate  of 
25.6  miles  per  hour  and  the  engine  is 
working  at  such  a  rate  that  it  will  carry 
the  train  up  a  0.4-per-cent  grade,  yet 
when  climbing  up  a  1. 0-per-cent  grade 
it  consumes  its  kinetic  energy  in  over- 
coming the  additional  grade.  When  it 
reaches  C,  it  has  lost  the  additional 
kinetic  energy  which  it  gained  from  A 
to  B,  and  as  it  continues  it  loses  even 
more.  When  it  reaches  Z),  it  has  lost 
4.8  feet  more  and  its  velocity  head  is 
reduced  to  14.05-4.8  =  9.25  feet,  which 
corresponds  to  a  velocity  of  16.2  miles 
per  hour.  At  D  the  grade  changes  to 
+0.1  per  cent. 

Here  we  have  the  rather  surprising 
condition  that,  although  the  grade  is 
actually  rising,  it  is  virtually  a  down- 
grade under  the  given  conditions,  for  the 
engine  is  working  harder  than  is  required 
to  run  up  merely  a  0.1-per-cent  grade  and 
hence  will  gain  in  velocity.  At  E,  a  dis- 
tance of  1600  feet  from  D,  it  reaches 
what  would  have  been  a  uniform  0.4-per- 


246 


RAILROAD  ENGINEERING  235 

cent  grade  from  A  to  E  and  the  grade  continues  at  that  rate. 
Although  the  train  has  actually  climbed  1 .6  feet  from  D  to  E,  it  has 
virtually  fallen  the  4.8  feet  between  D  and  D',  and  the  velocity 
head  has  increased  from  its  value  of  9.25  feet  at  D  to  14.05  feet, 
and  its  velocity  is  again  20  miles  per  hour.  The  upper  line  repre- 
sents the  'Virtual  profile",  which  may  always  be  drawn  by  measur- 
ing off  to  the  proper  scale  at  every  point  an  ordinate  which  is  the 
velocity  head  at  that  point.  Since  the  engine  is  working  uniformly, 
the  virtual  profile  is  in  this  case  a  straight  line. 

Although  the  variation  of  resistance  and  tractive  effort  with 
velocity  will  have  some  effect  on  the  precision  of  the  above  figures, 
as  discussed  later,  yet  the  demonstration  must  not  be  considered  as 
fanciful  and  impractical.  Under  the  given  conditions  it  is  sub- 
stantially what  would  take  place.  If  the  grade  B  D  were  continued 
to  Fj  or  until  the  actual  grade  intersected  the  virtual  profile,  the 
train  would  become  stalled,  for  when  the  engine  is  loaded  for  an 
indefinite  haul  up  a  0.4-per-cent  grade,  it  cannot  haul  a  train  indefi- 
nitely up  a  higher  grade.  Practically  the  train  would  stall  some- 
what short  of  F,  since  the  tractive  resistance  increases  as  the  velocity 
drops  to  nearly  zero.  Under  such  conditions,  B  D  is  sl  ''momentum 
grade",  which  may  be  higher  than  the  ruling  grade,  and  yet  it  is 
practically  harmless  under  these  conditions,  provided  that  a  train  is 
never  required  to  stop  on  that  grade.  A  B  C  is  technically  a  "sag" 
in  the  grade  A  C  and  would  be  considered  such  even  ii  A  B  were 
an  upgrade  (although  less  than  the  grade  A  C).  Such  a  sag  is 
usually  harmless  unless  it  is  so  deep  that  the  train  would  acquire  a 
dangerously  high  velocity  at  the  bottom  of  the  sag  B. 

In  the  above  numerical  case  the  velocity  is  only  25.6  miles  per 
hour,  w^hich  is  not  at  all  dangerous  even  for  freight  trains  in  these 
days  of  air  brakes  and  automatic  couplers.  But  a  much  deeper 
sag  might  require  the  use  of  brakes,  which  not  only  consumes  some 
of  the  energy  stored  in  the  train,  but  also  wears  out  the  wheel  treads 
and  brake  shoes. 

Another  phase  of  the  question  is  developed  when  we  consider 
the  action  of  a  train  stopping  on  a  grade.  Assume,  as  in  Fig.  158, 
that  a  train  is  climbing  up  the  grade  A  B  at  sl  uniform  velocity 
whose  velocity  head  is  measured  by  A  A'  =  B  B' .  At  B  it  com- 
mences to  slow  up  for  a  stop  at  C.    Since  it  is  stationary  at  C,  the 

247 


236 


RAILROAD  ENGINEERING 


velocity  head  is  zero  and  the  virtual  profile  A'  B'  runs  from  B'  to 
C  by  a  line  which  may  or  may  not  be  straight.  Assume  that  the 
train  starts  up  and. the  engine  exerts  such  force  that  at  J)  it  has 
regained  the  velocity  it  had  dit  A  ov  B.  The  ordinate  D  D'  must 
equal  A  A'  and  the  virtual  profile  must  run  from  C  to  D' .  C  D' 
therefore  represents  the  virtual  grade  up  which  the  train  must 
climb.  To  put  it  in  figures:  Ass-ume  that  C  D  =  1300  feet;  the 
required  velocity  at  D  is  20  miles  per  hour,  and  therefore  D  D'  = 
14.05;  the  grade  of  C  i)  is  1.0  per  cent  and  therefore  DD"  =  \Z 
feet,  and  D''  D' =  27.05  feet;  the  virtual  grade  CD'  is  therefore 
2.08  per  cent  instead  of  the  actual  1.0  per  cent  and  these  figures 
represent  the  actual  ratio  of  the  drawbar  pulls  at  the  engine. 


Fig.  158.     Diagram  Showing  Action -of  Forces  on  Train  Stopping  on  Grade 


To  be  more  precise,  the  virtual  grade  C  D'  will  not  be  a  uniform 
grade  as  shown  in  the  figure  but  will  be  a  curved  line  wh;ch  will  be 
steeper  at  the  beginning  of  the  grade  on  account  of  the  increased 
resistance  to  traction  when  starting.  This  is  somewhat  compen- 
sated by  the  fact  that  the  tractive  force  of  the  engine  is  greater  at 
the  very  low  velocities.  It  requires,  however,  a  little  margin  for 
safety. 

The  fact  that  the  engine  can  increase  its  velocity  from  zero  to 
20  miles  per  hour  in  that  distance  and  on  that  grade  shows  that  it 
is  capable  of  doing  much  more  than  rini  its  train  up  the  1.0-per- 
cent grade  at  a  speed  of  20  miles  per  hour.  In  fact,  unless  the 
power  is  reduced  when  the  train  reaches  D,  the  train  will  continue 
to  gain  velocity.  If  resistance  and  tractive  power  were  independent 
of  velocity,  the  train  would  continue  to  gain  indefinitely,  assuming 

248 


RAILROAD  ENGINEERING  237 

that  the  grade  continued  uniformly.  But  practically,  when  the  veloc- 
ity had  increased  to  a  much  higher  figure,  the  resistances  would 
increase  and  the  tractive  power  decrease  until  there  could  be  no 
further  incre^e  in  velocity. 

From  all  the  above  it  may  be  inferred  that 

(1)  When  the  velocity  is  uniform,  the  virtual  profile  is  parallel 
with  the  actual  profile. 

(2)  When  the  velocity  is  increasing,  the  profiles  are  separat- 
ing; when  it  is  decreasing,  they  are  approaching  each  other. 

(3)  When  the  velocity  is  zero  the  profiles  coincide. 

(4)  The  virtual  grade  at  any  place  is  a  measure  of  the  work 
required  of  the  engine  beyond  that  required  to  overcome  merely 
the  tractive  resistances.  If  it  is  horizontal  it  shows  that  the  engine 
is  doing  nothing  besides  overcoming  the  tractive  resistances.  If 
it  is  upward  and  is  uniform,  as  in  Fig.  157,  it  shows  that  it  is  work- 
ing uniformly  and  is  storing  in  the  train  "potential"  energy  which 
may  be  utilized  on  the  return  trip  if  it  is  not  utilized  in  moving 
down  a  succeeding  downgrade.  If  it  is  downward,  as  from  B' 
to  C,  Fig.  158,  it  shows  that  the  train  is  giving  up  kinetic  energy, 
probably  consuming  most  of  it  in  brakes,  but  utilizing  some  of 
it  to  furnish  the  tractive  power  to  run  from  B  to  C  and  also  to 
overcome  the  grade  from  B  to  C. 

181.  Use,  Value,  and  Possible  Misuse  of  Virtual  Profiles. 
It  has  been  previously  shown  that,  aside  from  securing  the  maxi- 
mum traffic,  the  most  important  accomplishment  for  the  locating 
engineer  is  to  obtain  low  ruling  grades.  At  the  same  time  the 
cost  for  grading  must  be  kept  as  low  as  possible  without  sacrificing 
the  more  important  elements.  The  grade  B  D  in  Fig.  157  is  an 
example  of  the  possibility  of  introducing  a  grade  which  is  much 
steeper  than  the  ruling  grade,  providing  it  is  not  so  long  that 
the  kinetic  energy  of  the  train  at  the  bottom  of  the  grade  is 
exhausted  before  it  reaches  an  easier  grade,  and  also  provided 
that  no  heavy  trains  are  ever  compelled  to  stop  on  that  grade. 
Herein  lies  the  danger  and  the   possible  misuse  of  this  method. 

A  grade  might  be  laid  out  substantially  as  shown  in  Fig.  157, 
with  the  intention  of  running  all  heavy  trains  up  that  grade  with- 
out stopping.  Later,  another  railroad  might  require  and  make  a 
grade  crossing  at  or  near  C,  which  would  occasionally  require  that 

249 


238  RAILROAD  ENGINEERING 

trains  shall  stop  at  the  crossing,  and  such  loaded  trains  would  be 
unable  to  start  against  such  a  grade,  especially  since  the  tractive 
resistance  to  starting  is  so  much  greater  than  the  resistance  at 
ordinary  speeds.  The  chief  value  of  such  a  method  lies  in  the  fact 
that  it  enables  the  engineer  to  determine  the  actual  demand  on  the 
locomotive,  as  it  is  affected  by  the  velocity  of  the  train.  The 
''undulatory"  profile  shown  in  Fig.  157  will  probably  be  much 
cheaper  to  construct  than  the  uniform  grade  A  E  which  would 
involve  a  fill  at  B  and  a  cut  at  D.  The  method  of  a  virtual  profile 
will  show  at  once  whether  ^uch  a  profile  at  that  place  will  be  a 
permissible  way  of  economizing  in  spite  of  the  fact  that  it  intro- 
duces a  1-per-cent  grade  which  is  perhaps  higher  than  the  ruling 
grade.  Many  of  the  "improvements  of  old  lines"  depend  on  this 
process  for  their  solution. 

For  example,  a  grade  which  always  may  have  been  harm- 
less and  unnoticed  suddenly  becomes  important  when  it  becomes 
desirable  or  necessary  to  require  all  heavy  trains  to  stop  at  some 
point  on  it;  such  a  ease  is  sketched  in  Fig.  158.  The  above  method 
indicates  how  such  a  problem  may  be  investigated.  The  grade 
C  D'  of  course  becomes  the  critical  grade,  but  under  given  con- 
ditions the  virtual  profile  will  show  the  demand  on  the  locomotive. 
Examples  of  this  w^ill  be  given  later.  Undulatory  grades  have 
the  advantage  of  decreasing  the  cost  of  construction  and  of  being 
harmless  under  given  conditions,  but  there  are  some  dangers. 

C  D  Em  Fig.  157  is  called  a  "hump"  in  the  grade.  In  the  numer- 
ical case  given  it  is  only  4.8  feet  and  would  be  harmless  under  almost 
any  conditions,  but  if  it  were  considerably  more,  and  if  a  train 
when  passing  C  had  a  velocity  much  less  than  20  miles  per  hour, 
it  might  become  stalled  before  reaching  the  summit  of  the  hump. 
Slippery  rails  or  a  strong  head  wind  may  so  increase  the  resistances 
against  which  a  train  works  that  if  the  computed  margin  of  velocity 
head  at  the  top  of  a  hump  is  made  too  small  it  may  be  entirely 
overcome  and  the  train  may  be  stalled  before  it  is  safely  over  the 
hump.  A  velocity  of  5  miles  per  hour,  which  corresponds  to  a 
velocity  head  of  only  0.88  feet  is  the  least  margin  that  should  be 
safely  allowed.  This  is  also  partly  due  to  the  fact  that  when  the 
velocity  becomes  less  than  5  miles  per  hour  the  resistances  per 
ton  increase,  and  as  the   velocity   drops  very  low   they  increase 

250 


RAILROAD  ENGINEERING  ^39 

very  rapidly  and  the  law  on  which  the  above  calculations  are  based 
becomes  inoperative. 

Another  danger  is  that  a  sag  may  be  so  deep  that  trains  will 
acquire  an  excessive  velocity  when  passing  through  it  unless  brakes 
are  applied.  This  of  course  does  not  mean  that  the  sag  must  not 
be  used.  It  simply  means  that  the  sag  will  cause  a  waste  of  energy 
in  brakes,  a  waste  which  must  afterward  be  made  up  by  increased 
work  from  the  locomotive.  This,  consequently,  is  one  of  the  cases 
which  requires  computation,  by  methods  which  follow,  to  determine 
whether  or  to  what  extent  the  sag  is  justifiable  so  that  the  two 
items  of  increased  first  cost  and  increased  operating  expenses  shall 
be  made  a  minimum.  For  example,  a  freight  train  may  approach 
a  sag  with  a  velocity  of  20  miles  per  hour.  Its  velocity  head  is 
therefore  14.05  feet.  If  the -sag  at  its  lowest  point  is  40  feet  lower 
than  the  imaginary  grade  line  on  which  the  train  could  have  run 
without  changing  its  velocity  (the  grade  ^  J5'  in  Fig.  157),  then  the 
velocity  head  of  the  train  at  the  bottom  of  the  sag  would  be  54.05 
feet,  which  corresponds  to  a  speed  of  39.2  miles  per  hour.  Although 
this  is  a  permissible  speed  with  freight  trains  which  are  equipped 
with  air  brakes  and  automatic  couplers,  it  is  approaching  the  limit, 
and  there  might  be  some  local  conditions  which  would  render  even 
this  speed  through  the  sag  inadvisable. 

182.  Problems.  1.  If  a  train  is  running  uniformly  along 
a  level  grade  at  a  speed  of  35  miles  per  hour  and  reaches  a  1.2-per- 
cent upgrade,  how  far  up  the  grade  could  it  run  before  its  speed  is 
reduced  to  10  miles  per  hour? 

Velocity  head  for  35  miles  per  hour  =  43.01  feet 
Velocity  head  for  10  miles  per  hour=  3.51  feet 

Permissible    increase     in    elevation  =  39.50  feet 
Distance  from  bottom  of  grade  =  39.50 ^.01 2  =  3292.  feet 

2.  At  what  speed  may  a  train  approach  a  sag  28  feet  below 
the  normal  grade  line  so  that  its  maximum  speed  at  the  bottom  of 
the  sag  shall  not  exceed  36  miles  per  hour? 

At  36  miles  per  hour  the  velocity  head  =  45.51  feet 
Subtracting  the  depth  of  the  sag  =  28.00  feet 

The  permissible  velocity  is  that  due  to  17.51  feet  or  22.3  miles 
per  hour. 

251 


240  RAILROAD  ENGINEERING 

RESISTANCES 

183.  Train  Resistance.  The  energy  of  the  steam  in  the  loco- 
motive boiler  is  spent  first  in  overcoming  the  various  internal  resist- 
ances between  the  boiler  and  the  rims  of  the  driving  wheels.  This 
engine  resistance  is  computed  later.  Then  the  resistance  due  to 
the  truck  wheels  of  engine  and  tender  and  the  atmospheric  resist- 
ance together  make  up  the  difference  (on  a  level  track  and  at  uni- 
form velocity)  between  the  adhesion  at  the  drivers  and  the  draw- 
bar pull.  The  draw-bar  pull  is  spent,  as  discussed  herewith,  in 
overcoming  the  effect  of  (1)  grade,  (2)  curvature,  (3)  the  normal 
track  resistance  on  a  straight-level  track  at  uniform  velocity,  (4) 
the  force  required  to  accelerate  and  (5)  the  starting  resistance. 

(1)  Grade  Resistance.  Grade  resistance  is  readily  determin- 
able with  mathematical  accuracy  and  equals  20  pounds  per  ton 
(of  2000  pounds)  for  each  per  cent  of  grade.  For  example,  the  grade 
resistance  on  a  1.2-per-cent  grade  is  20X1.2  =  24  pounds  per  ton. 

(2)  Curvature  Resistance.  Curvature  resistance  is  usually  con- 
sidered to  be  the  equivalent  of  a  .035-per-cent  grade  for  each  degree 
of  curvature,  although  the  resistance  varies  somewhat,  depending 
on  the  velocity,  and  on  the  superelevation  of  the  outer  rail,  the 
resistance  being  greater  if  the  velocity  is  much  less  than  that  for 
which  the  superelevation  was  designed.  This  is  the  value  usually 
taken  in  computing  the  compensation  for  curvatures  (see  article 
176).  Then  the  resistance  in  pounds  per  ton  equals  20 X. 035  =  0.7 
pound  for  each  degree  of  curvature.  • 

Examples.    1 .   What  is  the  curvature  resistance  per  ton  on  a  4-degree  curve? 
Solution.  4  X 0.7  =  2.8  pounds  per  ton 

'2.  What  is  the  combined  curvature  and  grade  resistance  on  a  6-degree 
curve,  located  on  a  2.2-per-cent  grade? 

Solution.  The  grade  equivalent  to  the  curve  =  6X -035  =  0.21,  which  added 
to  2.2=2.41  per  cent,  the  equivalent  grade.  20X2.41=48.2  pounds  per  ton, 
the  resistance. 

(3)  Normal  Track  Resistance.  Normal  track  resistance  is  a 
combination  of  several  resistances  which  are  variously  affected  by 
changes  in  conditions.  The  resistance  to  the  rolling  of  wheels  on  the 
rails  is  a  very  small  part  of  the  total  resistance.  Accurate  tests  of 
journal  friction  show  that  the  friction  of  axles  in  their  bearings  is 
actually  less  at  higher  velocities,  probably  because  the  resulting  higher 

252 


RAILROAD  ENGINEERING  241 

temperature  reduces  the  friction.  The  total  varies  with  the  number 
of  cars  in  the  train.  The  resistance  per  ton  is  much  lower  as  the 
load  per  wheel  increases.  The  atmospheric  resistance  of  freight 
trains  evidently  depends  on  whether  the  train  is  made  up  of  only 
one  type  of  car  (box,  flat,  or  gondola),  or  of  a  combination  of  types, 
which  would  increase  that  resistance.  Numerous  experiments  have 
been  made,  by  placing  a  dynamometer  between  the  locomotive  and 
first  car,  to  determine  the  amount  of  the  tractive  force  and  to  dis- 
cover its  variation  with  velocity  and  its  other  laws.  Of  course  it 
was  necessary,  when  analyzing  the  results  of  these  tests,  to  deduct 
first  the  effect  of  grade,  curvature,  and  acceleration  or  retardation; 
but  even  then  the  results  are  so  far  from  uniform  that  no  set  of 
numerical  values  can  be  uniformly  applied  to  all  grades  of  track. 
This  variation  is  due  to  the  very  evident  fact  that  the  resistance 
would  be  less  on  a  high-grade,  well-kept  track,  with  heavy  rails  than 
on  a  cheap,  rough  track,  with  light  rails.  But  there  is  one  very 
significant  and  surprising  result  which  may  be  deduced  from  each 
series  of  tests,  and  that  is,  that  a  formula  which  makes  the  resistance 
equal  a  constant  times  the  number  of  tons  plus  another  constant 
times  the  number  of  cars,  but  with  no  variation  depending  on  veloc- 
ity, will  satisfy  the  dynamometer  results  as  closely  as  any  other 
equally  simple  law.  This  statement  applies  to  freight  trains  between 
the  velocities  of  5  miles  and  35  miles  per  hour.  When  starting  the 
resistance  is  greater.  At  higher  velocities  than  35  m.p.h.  the  resist- 
ance is  also  greater,  but  since  the  economies  of  reduced  resistance 
apply  chiefly  to  freight  trains  at  usual  working  velocities,  the  sim- 
plicity of  the  above  law  is  important.  Each  set  of  tests  on  any 
given  piece  of  track  will  give  a  new  pair  of  constants  for  the  resist- 
ance formula.  A  compilation  of  the  results  of  many  tests  gave  the 
following,  issued  by  the  American  Railway  Engineers  Association, 
as  an  average  formula: 

R  =  2.2  r+121.6C  (105) 

in  which  R  is  total  resistance  at  uniform  velocity  on  a  level  tangent; 
T  is  total  weight  of  cars  and  contents,  in  tons;  and  C  is  number  of 
freight  cars  in  train. 

It  should  be  clearly  understood  that  the  formula  does  not 
necessarily  give  the  actual  resistance  for  any  given  case,  since  the 

253 


242  RAILROAD  ENGINEERING 

resistance  will  depend  on  the  actual  condition  of  the  track,  but  the 
result  will  be  a  good  average  result  and  for  comparative  purposes  the 
formula  is  useful. 

The  resistance  of  trains  at  higher  velocities  than  35  miles  per 
hour  must  be  considered  as  depending  on  velocity.  The  formula 
used  by  the  Baldwin  Locomotive  Works  is 

7^  =  4.3+0.0017  V  (106) 

in  which  R  is  the  resistance  per  ton,  and  V  is  the  velocity  in  miles 
per  hour.  The  formula  is  particularly  applicable  to  passenger 
trains  having  cars  weighing  45  tons  and  over.  For  lighter  cars,  the 
freight-train  formula  should  be  used.  The  formula  should  not  be 
used  for  low  velocities,  especially  those  below  10  miles  per  hour, 
nor  for  light-weight  cars. 

Example.     Assume  that  there  are  33  freight  cars  weighing,  with  con- 
tents, 2200  tons.     What  is  the  total  resistance  behind  the  engine? 
Applying  equation  (105) 

/2  =  2.2  X 2200  + 121 .6  X  33  =  8853  pounds 

As  an  illustration  of  variations  in  results,  depending  on  varia- 
tions in  track  condition,  some  tests  on  the  Baltimore  &  Ohio  Railroad 
were  reduced  to  a  formula  similar  to  equation  (105)  but  with  the 
constants,  2.78  and  113.9.  Using  these  constants  and  applying  the 
formula  to  the  above  numerical  case,  the  computed  value  of  R 
would  be  9875,  an  increase  of  nearly  12  per  cent.  This  variation 
shows  the  uselessness  of  attempting  to  apply  any  definite  numerical 
values  and  to  expect  accuracy  unless  the  resistance  of  the  particular 
track  in  question  has  been  determined  by  actual  test. 

(4)  Accelerative  Force.  Accelerative  force  has  been  computed 
theoretically  in  article  179.  The  formula  for  acceleration  may  also 
be  applied  to  determine  how  far  the  kinetic  energy  in  a  train  will 
help  to  force  it  up  a  grade  which  is  greater  than  that  up  which 
the  locomotive  could  haul  such  a  train  indefinitely. 

(5)  Starting  Resistance.  As  previously  stated,  the  resistance 
per  ton  when  starting  a  train  is  considerably  in  excess  of  the  ordinary 
resistance.  When  cars  have  been  left  standing  for  several  hours, 
or  even  days,  especially  in  winter  weather,  it  may  take  a  force  of 
40  pounds  per  ton  to  produce  motion.  The  bearings  become 
"frozen".     But  such  resistance  is  only  momentary  and  may  be 

264 


RAILROAD  ENGINEERING  243 

partly  overcome  by  the  impact  of  moving  cars  or  engine  striking 
against  the  stalled  cars.  When  an  engineer  reverses  his  engine, 
backs  it  against  the  cars,  and  then  immediately  reverses  again  so 
as  to  go  forward,  he  accomplishes  three  things:  (1)  the  journals 
become  loosened  from  the  comparatively  rigid  condition  they  will 
assume  even  during  a  short  stop;  (2)  the  springs  of  the  couplers 
w  ill  become  compressed  during  the  small  backward  motion  and  their 
expansion  during  forward  motion  wdll  materially  assist  the  forward 
motion;  (3)  if  the  train  is  very  long,  the  total  slack  in  the  couplers 
is  very  considerable  and  the  locomotive  will  have  moved  several 
feet  before  the  last  car  begins  to  move  and  the  cars  are  started 
one  by  one.  Such  devices  in  operation  reduce  to  a  variable  extent 
the  resistance  which  would  be  encountered  if  all  cars  were  started 
at  the  same  instant.  A  series  of  tests  on  the  Rock  Island  system 
gave  results  with  an  ordinary  range  from  10  to  18  pounds  per  ton 
and  averaging  14.1  pounds.  An  extreme  value  of  30  pounds  was 
noted  for  ''frozen  bearings"  and  a  low  extreme  of  only  6  pounds 
extra  when  the  stop  was  only  momentary.  Since  a  juggling  of 
the  train  can  produce  virtually  the  same  result  as  a  mere  momen- 
tary stop,  the  necessary  extra  starting  resistance  for  a  limiting 
case  will  be  considered  as  only  6  pounds  per  ton  in  solving  some 
numerical  problems  in  a  later  article. 

Example.  How  much  draw-bar  pull  wiU  be  required  to  haul  a  freight 
train  of  10  cars,  each  weighing  70  tons,  and  a  caboose  weighing  lo  tons,  at  a 
uniform  velocity  of  15  miles  per  hour  up  a  0.9-per-cent  grade? 

Solution.  The  only  significance  of  the  15  m.p.h.  in  the  solution  is  the 
fact  that  it  is  between  5  and  35  and  that  equation  (105)  is  applicable.  The 
grade  resistance  per  ton  is  20X0.9  =  18  pounds,  and  for  the  11  cars  weighing 
715  tons  it  is  715X18  =  12,870  pounds.  The  tractive  resistance,  by  equation 
(105),  is 

72  =  2.2X715  +  121.6X11=2911  pounds 

Adding  the  gi-ade  resistance,  the  total  resistance  would  be  15,781  pounds. 

The  above  problem  assumed-  gondola  cars  weighing  40,000 
pounds  and-  each  carrying  100,000  pounds  and  a  15-ton  caboose. 
Suppose  that  the  train  consisted  of  empties,  say  35  empties  at  20 
tons  each,  or  700  tons,  and  the  15-ton  caboose.  The  total  weight 
being  the  same,  the  grade  resistance  is  the  same.  But  the  number 
of  cars  being  greater,  the  tractive  resistance  is  greater  and 

7^  =  2.2X715+121.6X36  =  5951  pounds 

255 


244  RAILROAD  ENGINEERING 

which  is  an  increase  of  3040  pounds,  and  the  tractive  resistance 
is  more  than  doubled.  It  should  be  noted  that  if  there  were  no 
grade,  the  tractive  resistance  would  be  only  2911  pounds  for  the 
loaded  train  and  5951  pounds  (over  twice  as  much)  for  the  empty 
train  of  the  same  gross  weight.  On  the  other  hand,  on  the  0.9-per- 
cent grade  the  resistance  of  the  loaded  train  would  be  15,781  pounds 
and  that  of  the  train  of  empties  5951  +  12,870  =  18,821  pounds, 
which  is  only  19  per  cent  greater.  The  average  tractive  resistance  per 
ton  of  the  loaded  train  is  2911-^-715  =  4.07  pounds,  while  that  of 
the  empty  train  is  5951 -r- 715  =  8.32  pounds.  The  grade  resistance 
is  constant  in  either  case  at  18  pounds  per  ton.  The  character 
of  the  train  load,  whether  loaded  or  consisting  of  a  long  train  of 
empties  of  the  same  gross  weight,  is  thus  a  matter  of  great  impor- 
tance on  a  level  or  nearly  level  road  and  becomes  of  much  less  impor- 
tance on  a  grade  of  even  0.9  per  cent.  On  a  2-per-cent  grade  the 
tractive  resistance  is  comparatively  small  and  variation  in  the 
character  of  the  loading  is  of  still  less  importance. 

Example.  How  much  tractive  force  will  be  required,  using  the  data  of 
the  previous  example,  to  increase  the  velocity  from  15  m.p.h.  to  20  m.p.h.  in 
a  distance  of  500  feet? 

Solution.  Applying  equation  (104)  we  have  Fi  =  15,  ¥.^  =  20,  and  s=  500. 
Then 

70 
P  =  ^(20^-15^)  =24.5  pounds  per  ton 

For  the  715-ton  train,  this  will  require  an  extra  pull  of  17,518 
pounds.  This  is  the  equivalent  of  a  24.5-^20=1.225-per-cent 
grade.  Whether  the  locomotive  has  sufficient  tractive  force  to 
pull  15,781  pounds  of  tractive  force  and  grade  resistance  and  17,518 
pounds  more  for  acceleration,  or  a  total  of  33,299  pounds,  is  a  matter 
to  be  studied  under  "power  of  the  locomotive",  article  189.  The 
further  question  would  arise,  could  the  locomotive  make  steam 
fast  enough  to  produce  this  energy?  This  will  be  considered  in 
article   189. 

Example.  What  is  the  tractive  resistance  behind  a  passenger  engine 
of  a  load  of  4  cars,  each  weighing  52  tons  and  traveling  at  a  velocity  of  60  miles 
per  hour? 

Solution.  Substituting  in  equation  (106)  the  value  of  F  =  60,  we  obtain 
R  =  10.42  pounds  per  ton,  and  for  the  208  tons  the  draw-bar  pull  would  be  2167 
pounds. 

256 


RAILROAD  ENGINEERING  245 

Irrespective  of  the  resistance  of  the  locomotive  itself,  considered 
later,  this  pull  of  2167  pounds  at  a  velocity  of  60  m.  p.  h.,  or  88  feet 
per  second,  is  the  equivalent  of  88X2167  =  190,696  foot-pounds  per 
second,  or,  dividing  by  550,  equal  to  346  horsepower. 

PULLEY  POWER  OF  LOCOMOTIVES 

184.  Rating  of  Locomotives.  Since  it  is  very  important  for 
the  economical  operation  of  roads  that  each  locomotive  should 
be  loaded  to  the  limit  of  what  it  can  efficiently  haul,  and  since, 
as  shown  in  article  183,  the  hauling  power  of  a  locomotive,  especially 
on  a  flat  grade,  depends  on  the  number  of  cars  as  well  as  on  their 
gross  weight,  it  is  important  to  determine  for  each  locomotive  a 
loading  which  will  measure  its  power  and  which  is  independent  of 
the  number  of  cars  or  of  the  rate  of  grade.  This  loading  is  called  its 
''rating"  and  by  applying  to  the  rating  a  proper  correction,  depending 
on  the  number  of  cars  and  grade,  the  hauling  power  or  the  proper 
loading  of  that  locomotive  for  any  grade  may  be  readily  determined. 

Let  P  be  pulling  powder  of  the  locomotive,  or  the  tractive  power 
as  measured  at  the  rim  of  the  drivers;  E  weight  of  engine  and  tender, 
in  pounds;  W  weight  of  cars  behind  tender,  in  pounds;  R  rate  of 
grade,  or  ratio  of  vertical  to  horizontal;  K  a  constant  which,  as 
determined  by  tests,  is  the  factor  2.2  pounds  per  ton,  in  equation 
(105);  C  a  constant  which,  as  determined  by  tests,  is  the  factor 
121.6  pounds  per  ton,  in  equation  (105);  N  number  of  cars  in  the 
train;  and  A  the  desired  rating.     Then 

P={E+W)  {R+K)^NC 
transforming. 


R+K  '      R-\-K 

The  right-hand  side  of  this  equation  is  the  weight  of  the  train 
behind  the  tender  plus  the  number  of  cars  times  a  quantity  made 
up  of  two  constants  and  the  rate  of  grade.  This  right-hand  side 
of  the  equation  is  called  the  rating,  or  A.  Values  of  the  fraction 
C-i-{R-\-K),  in  tons  per  car,  which  are  independent  of  engine  or 
train  characteristics,  are  tabulated  for  various  rates  of  grade,  as 
given  in  Table  XVIII.  In  computing  these  values,  since  C  and  A' 
are  resistances  per  ton,  R  must  be  the  resistance  Der  ton  for  the 
rate  of  grade  considered. 


246 


RAILROAD  ENGINEERING 


TABLE  XVI H 
Values  of  C-7-(R-\-K)  for  Various  Grades 

(In  tons  per  car) 


Grade 

R 

(per  cent) 

Tons 

Grade 

R 

(per  cent) 

Tons 

Grade 

Tons 

Grade 

Tons 

Grade 

Tons 

PER  Car 

PER  Car 

R 

PER  C.\.R 

R 

per  Car 

R 

per  Car 

(R+K) 

(R+K) 

(per 
cent) 

C-r 

iR+K) 

(per 
cent) 

C^ 

iR+K) 

(per 
cent) 

(R+K) 

Level 

55 

0.5 

10.0 

1.0 

5.5 

1.5 

3.8 

2.0 

2.88 

0.1 

29 

0.6 

8.5 

1.1 

5.0 

1.6 

3.6 

2.1 

2.75 

0.2 

20 

0.7 

7.5 

1.2 

4.6 

1.7 

3.4 

2.2 

2.63 

0.3 

14 

0.8 

6.7 

1.3 

4.3 

1.8 

3.2 

2.3 

2.52 

0.4 

12 

0.9 

6.0 

1.4 

4.0 

1.9 

3.0 

2.4 

2.42 

Examples.  1.  Assume  that  the  pulling  power  P  of  a  locomotive,  or  the 
power  at  the  rim  of  the  drivers,  computed  as  in  article  190,  was  estimated  to 
be  33,742  pounds  and  that  the  weight  E  of  the  engine  and  tender  was  315,000 
pounds.  On  a  0.5-per-cent  grade  R  =  .005  and  K  =  2.2  pounds  per  ton  or  .0011 
pound  per  pound. 

Solution. 

P  ^^  74-9 

A=^^^-E=  ^^:\;^,, -315,000  =  5,216,000  pounds  =  2608  tons 

il-f-zl  .OUo  +  .LMJll 

which  is  the  rating  for  a  0.5-per-cent  grade.  Similar  ratings  for  that  locomotive 
may  be  easily  computed  for  all  rates  of  grade.  Such  a  locomotive  may  haul 
on  any  grade  a  load  W  such  that  A=W+N  C-=-(fl+K).  From  Table  XVIII 
we  find  that,  for  a  0.5-per-cent  grade,  C-^{R+K)  =  10.  If  there  are  40  cars  in 
the  train,  then 

2608  =  TF-f- (40X10) 

W  =  2608  -  400  =  2208  tons 
which  is  an  average  of  55  tons  per  car.     If  the  cars  are  of  uniform  weight  (such 
as  empties,  weighing  say  18  tons)  then  W  =  1S  N,  and  the  equation  becomes 

2608  =  18  iV  +  10  AT  =  28  AT 
and 

iV=93 
which  means  that  such  an  engine  can  haul  a  load  of  93  empties,  each  averaging 
18  tons,  up  a  0.5-per-cent  grade  at  a  uniform  velocity.     Note  that  this  ignores 
curvature  resistance,  which  if  it  exists  is  assumed  to  be  provided  by  a  com- 
pensation of  the  grade. 

2.     What  would  be  the  rating  for  the  same  locomotive  on  a  long  1.6-per- 
cent grade? 
Solution. 

33,742 


A  = 


315,000  =  1,658,000  pounds  =  829  tons 

Again  considering 


.016  +  .0011 
By  Table  XVIII,  the  "adjustment"  in  tons  per  car  is  3.6 
empties  weighing  18  tons,  we  would  have 

829  =  18  A^+3.6iV  =  21.6  AT 
and 

N  =  SS 


258 


RAILROAD  ENGINEERING  247 

If  all  cars  were  loaded  and  had  an  average  weight  of  56  tons,  we  would  have 
829  =  56  Ar+3.6  i\r  =  59.6  N 
A'' =  nearly  14,  or  say  13  loaded  cars  and  the  caboose 

In  the  above  examples  the  pulUng  power  P  is  determined  on 
the  basis  of  the  locomotive  working  at  the  maximum  velocity  M  at 
which  it  can  maintain  full  stroke.  See  article  190.  This  represents 
practically  the  maximum  power  of  the  locomotive.  The  velocity 
M  is  usually  from  4  to  7  miles  per  hour  and  is  as  low  as  should  be 
allowed  on  maximum  grades,  since  an  attempt  to  utilize  a  slightly 
higher  tractive  force  at  a  somewhat  lower  velocity  would  probably 
result  in  stalling  the  train  if  an  unexpected  resistance  in  the  track 
slightly  increased  the  normal  resistance. 

185.  Units  of  Operation.  A  large  part  of  the  calculations  in 
railroad  economics  consists  of  a  valuation  of  changes  in  alinement 
or  the  financial  value  of  a  reduction  of  distance,  curvature,  rise  and 
fall,  and  ruling  grade.  Formerly  such  calculations  were  made 
exclusively  on  the  basis  of  the  cost  of  an  average  train-mile^  especially 
as  this  is  shown  to  be  surprisingly  constant  for  roads  of  all  charac- 
ters, long  and  short,  heavy  traffic  and  light  traffic.  The  general 
method  was  to  take  up  each  item  in  turn  of  the  average  cost  of 
operating  trains  and  to  estimate  the  effect  of  a  change  in  alinement 
on  the  normal  average  percentage  of  each  item.  Some  of  the  items 
are  affected  very  materially;  others  are  affected  very  little  or  not  at 
all.  The  normal  average  for  each  item  was  then  multiplied  by  the 
percentage  by  which  that  item  was  estimated  to  be  affected  by  that 
unit  change  in  alinement  conditions,  and  then  the  sum  of  these  prod- 
ucts would  be  the  computed  percentage  by  which  that  unit  change 
of  alinement  would  affect  the  average  cost  of  a  train-mile.  Further 
study  has  shown  that  the  cost  of  fuel,  for  example,  for  freight  trains 
is  disproportionately  high.  Therefore,  when  comparing  the  rela- 
tive costs  of  operating  freight  locomotives  on  two  different  grades, 
it  will  not  do  to  base  the  estimate  of  increased  fuel  demand  on  the 
average  cost  of  fuel  for  locomotives  of  all  kinds.  But  it  has  become 
increasingly  apparent  that  the  effect  of  grade,  for  example,  on  the 
cost  of  operating  a  train  is  largely  dependent  on  the  weight  of  the 
train,  on  the  character  of  the  locomotive  and  its  rating.  Therefore 
the  effect  of  grade  cannot  be  measured  by  any  one  factor  times  the 
number  of  train  miles  involved. 


259 


248  RAILROAD  ENGINEERING 

Some  of  the  elements  of  variation  of  operating  expenses  are 
more  accurately  measured  by  the  number  of  ton-miles.  A  study  of 
the  effect  of  rolling  stock  on  track  maintenance  shows  that  it  is 
largely  dependent  on  train  velocity  and  also  on  intensity  of  axle 
loading.  Although  exact  ratios  are  not  computable,  it  has  been 
broadly  estimated  that  passenger  trains,  having  a  much  higher 
average  velocity,  are  responsible  for  twice  as  much  track  damage 
as  the  same  tonnage  of  freight  trains;  also  that  locomotives,  having 
heavier  axle  loads  and  not  being  truly  counterbalanced,  are  respon- 
sible for  twice  as  much  track  damage  as  the  cars  of  the  same  train, 
which  w^ould  mean  that  the  locomotive  of  a  high-speed  passenger 
train  would  do  four  times  as  much  damage  as  the  car  axles  of  a  slow 
freight. 

The  passenger-mile,  although  frequently  used  in  statistics  of 
service  rendered  by  railroads,  has  little  or  no  relation  to  the  cost  of 
service  and  therefore  is  not  used  in  problems  of  changes  in  alinement 
and  grade. 

The  car-mile  is  a  useful  unit  for  some  special  purposes.  If  a 
steel  passenger  car  weighs  100,000  pounds  and  carries  even  its 
maximum  load  of  80  passengers  with  an  average  weight  of  125 
pounds,  the  total  live  load  (10,000  pounds)  is  only  10  per  cent  of  the 
dead  load.  And  when,  as  is  usual,  the  actual  live  load  is  only  a 
part,  and  perhaps  a  small  part,  of  the  possible  load,  then  it  makes 
but  little  difference  in  the  tractive  force  required  for  hauling,  espe- 
cially on  low  grades,  whether  the  car  is  loaded  or  empty.  Other 
items  of  expense  vary  almost  directly  as  the  number  of  car-miles. 

The  engine-mile  is  similarly  a  useful  unit  in  estimates  in  which 
certain  costs  vary  as  the  number  of  engine-miles  and  nearly  or  quite 
regardless  of  variations  in  other  factors. 

Another  element  of  practical  cost  in  the  operation  of  trains 
over  a  division  is  the  total  time  required  for  a  run  by  the  slow  freight 
trains.  The  old  methods  would  invariably  indicate  that  the- most 
economical  grades,  using  locomotives  of  a  certain  power,  were  those 
which  would  permit  the  maximum  train  load,  even  at  the  slowest 
velocity.  But  it  was  later  developed  that  it  is  actually  more  econom- 
ical to  run  somewhat  lighter  trains  at  a  higher  velocity;  and  that 
there  is  a  certain  combination  of  train  load  and  velocity  beyond 
which,  if  the  train  load  is  increased  and  the  time  of  run  increased. 


260 


RAILROAD  ENGINEERING  249 

the  extra  fuel  burned,  the  extra  time  of  the  train  crews,  and  the 
extra  blocking  of  the  tracks  (especially  on  a  single-track  road)  more 
than  offset  the  economy  of  increased  tonnage  in  one  train.  A  con- 
sideration of  these  various  elements  and  units  of  operation  shows 
the  impracticability  of  adopting  any  uniform  unit  values  for  one 
foot  (or  mile)  of  distance  saved,  or  of  one  degree  of  curvature  saved, 
or  for  each  fV  per  cent  of  grade  lowered,  which  would  be  sufficiently 
accurate  for  universal  applicability,  and  that  the  only  accurate 
method  of  studying  the  value  of  a  proposed  change  of  alinement  for 
handling  an  assumed  amount  of  business,  with  an  assumed  type  of 
locomotive,  is  to  estimate  the  power  of  that  locomotive  on  each  of 
the  two  grades  (or  other  variations  of  alinement)  and  the  relative 
number  of  trains,  with  their  cost  of  operation,  in  order  to  handle 
that  business.  If  the  problem  is  a  suggested  change  in  an  existing 
road,  the  investigator  has  the  advantage  of  an  opportunity  to  study 
what  the  locomotive  in  use  can  do  on  the  existing  alinement  and 
grades,  and  he  has  only  to  compute  the  effect  of  the  changes.  If 
the  problem  is  a  suggested  change  in  a  proposed  new  line,  the  cost 
of  operation  under  both  conditions  must  be  estimated. 

186.  Types  of  Locomotives.  The  variations  in  locomotive 
service  have  developed  all  conceivable  types  as  to  total  weight, 
ratio  of  total  weight  to  weight  on  drivers,  types  of  running  gear, 
relation  of  steaming  capacity  to  tractive  power,  etc.  The  method 
of  classification  on  the  basis  of  the  running  gear  is  very  simple. 
The  number  of  wheels  on  both  rails  of  the  pilot  truck,  if  any,  is 
placed  as  the  first  of  three  numbers.  If  there  is  no  pilot  truck,  the 
character  0  is  used.  This  is  followed  by  the  number  of  drivers  and 
then  by  the  number  of  trailing  wheels,  if  any.  For  example,  a 
Pacific-type  engine  has  four  wheels  on  the  pilot  truck,  six  driving 
wheels,  and  two  trailing  wheels  under  the  rear  of  the  boiler.  The 
wheel  base  is  symbolized  as  4-6-2.  The  most  common  types  of 
locomotives,  with  their  popular  names  and  wheel-base  symbols,  are 

2-8-0 

2-8-2 

4-8-0 

2-10-2 

A-B-B-A 

1,  usually       2  or  0 

Six-wheel  switcher   0-6-0  B=  drivers,  varying  from    4  to  10 

261 


American 

4-4-0 

Consolidation 

Columbia 

2-4-2 

Mikado 

Atlantic 

4-4-2 

Mastodon 

Mogul 

2-6-0 

Santa  Fe 

Ten-wheel 

4-6-0 

Mallet 

Pacific 

4-6-2 

A  =  truck  w. 

250  RAILROAD  ENGINEERING 

The  Interstate  Commerce  Commission  report  for  1912  showed 
534  locomotives  of  the  *'Mallet"  type,  out  of  a  total  of  62,262  in  the 
U.  S.  This  is  less  than  1  per  cent  but,  considering  that  the  growth 
in  numbers  of  this  type  in  one  year  was  nearly  23  per  cent  while  the 
increase  in  all  classes  was  about  IJ  per  cent,  or  that  more  than  10 
per  cent  of  the  net  increase  was  of  this  type,  it  deserves  special  men- 
tion. Excluding  freak  variations,  they  are  always  "four-cylinder 
compounds",  one  pair  of  cylinders  discharging  into  the  other  pair 
and  then  exhausting.  They  have  from  five  to  ten  driving  axles, 
and  have  a  length  of  engine  wheel-base  up  to  nearly  60  feet.  Some- 
times the  boiler  is  made  ''flexible"  by  a  set  of  accordion-shaped 
steel  rings  forming  a  joint  in  the  boiler  shell.  The  boiler  proper  is 
on  one  side  of  the  joint  and  the  feed-water  heater,  the  reheater,  and 
perhaps  the  superheater  are  on  the  other  side.  Or,  the  boiler  shell 
is  made  rigid,  one  end  is  rigidly  attached  to  the  frame  carrying  the 
high-pressure  cylinders  and  the  other  end  is  supported  on  a  bearing 
on  the  truck  frame  which  carries  the  low-pressure  cylinders  and  the 
drivers  operated  by  them.  The  low-pressure  truck  frame  swings 
around  a  pivot  in  the  fixed  frame  and  this  so  cuts  down  the  length 
of  rigid  wheel-base  that  these  engines  are  operated  successfully  on 
20-degree  curves,  and  are  therefore  practicable  on  any  road  having 
reasonable  alinement.  These  locomotives  are  chiefly  used  by  roads 
handling  large  quantities  of  heavy  freight,  such  as  coal,  up  long 
stretches  of  heavy  grades,  where  the  demand  for  tractive  power  is 
very  great.  The  tractive  power  of  some  of  these  locomotives  is 
over  110,000  pounds,  which  is  nearly  four  times  as  great  as  that  of 
the  average  locomotive  in  the  United  States. 

187.  Oil=Burning  Locomotives.  In  1912  over  one-sixth  of 
all  the  locomotives  west  of  the  Mississippi  River  used  oil  as  fuel. 
Some  of  the  advantages  in  using  oil  are  as  follows:  (1)  the  British 
thermal  units  in  one  pound  of  oil  vary  from  about  19,000  to  21,000; 
those  in  a  pound  of  coal  vary  from  perhaps  14,000  down  to  5000  for 
the  poorer  grades  of  lignite  found  in  the  western  part  of  the  United 
States  and  this  means  a  great  reduction  in  the  cost  of  carrying  and 
storing  fuel,  measured  in  heat  units;  (2)  the  cost  of  handling  fuel  is 
reduced  and  that  of  disposing  of  ashes  is  eliminated;  (3)  engine 
repairs  are  reduced  in  many  respects  although  it  is  said  that  the 
increased  cost  of  fire-box  repairs,  due  to  the  intense  heat  of  the  oil 

262 


RAILROAD  ENGINEERING  251 

flame,  offsets  any  reduction  in  other  items;  (4)  the  fires  can  be  more 
easily  controlled  and  waste  of  heat  reduced  during  stoppages  or 
when  drifting  down  grade;  (5)  wayside  fires  due  to  sparks  are  alto- 
gether eliminated;  (6)  there  is  a  practical  limitation  (see  article 
189)  to  the  amount  of  coal  that  one  fireman  can  feed  to  a  fire,  but 
there  is  no  such  limitation  when  using  oil;  (7)  there  is  an  equality 
in  cost  of  heat  units  when  a  42-gallon  barrel  of  oil,  weighing  7.3 
pounds  per  gallon,  costs  60  cents  and  a  ton  (2000  pounds)  of  coal, 
having  two-thirds  as  many  heat  units  per  pound,  costs  $2.61,  or 
4.35  times  as  much.  The  other  items  of  difference  almost  invariably 
favor  the  oil  and  might  make  it  more  desirable  even  when  the  ratio 
of  cost  seemed  to  favor  the  coal.  Oil  is  used  very  extensively  west 
of  the  Mississippi  River,  where  in  many  places  oil  is  plentiful 
and  cheap  and  coal  is  poor  in  quality  and  high  in  price. 

188.  Relation  of  Type  to  Service  and  to  Track  Conditions. 
Economy  in  operating  conditions  requires  a  thorough  co-ordination 
between  the  characteristics  of  the  locomotive,  the  fuel  it  is  to  burn, 
the  roadbed  and  track  it  is  to  run  on,  and  the  character  of  service 
it  is  to  render.  It  may  not  even  be  the  best  economy  to  use  the 
same  type  of  locomotive,  for  a  given  kind  of  service,  on  consecutive 
divisions  of  the  same  road. 

IV heel- Load  to  Rail-Weight.  Since  the  support  w^hich  the  rail 
receives  from  the  ties  and  ballast  is  uncertain  and  variable,  any 
rule  for  the  relation  must  be  empirical  and  approximate.  The  rule 
adopted  by  the  Baldwin  Locomotive  Works  ("300  pounds  of  wheel 
per  pound  of  rail  per  yard")  may  be  used  in  making  a  diagram  from 
which  the  relation  between  total  weight  on  driving  wheels,  number 
of  drivers,  and  weight  of  rail,  may  be  readily  observed.  Fig.  159. 

For  example,  if  it  is  desired  to  use  a  type  of  locomotive  with 
170,000  pounds  on  the  drivers  and  also  75-pound  rails,  four  pairs 
of  drivers  will  be  needed.  By  using  95-pound  rails  the  same  weight 
on  drivers  could  be  placed  on  three  axles.  As  another  example, 
a  Pacific-type  locomotive,  with  150,000  pounds  on  its  six  drivers, 
should  have  a  rail  with  a  minimum  weight  of  83  pounds,  or  say 
an  85-pound  rail. 

189.  Power  of  Locomotives.  The  tractive  power  of  a  loco- 
motive, or  its  *'draw-bar  pull"  is  limited  by  the  adhesion  of  the 
drivers,  and  by  the  capacity  of  the  boiler  to  make  steam.    The 

263 


252 


RAILROAD  ENGINEERING 


adhesion  of  the  drivers  is  a  fairly  definite  ratio  of  the  weight  on 
the  drivers.  Under  very  favorable  conditions,  with  a  dry  rail 
and  using  sand,  a  ratio  of  one-third  and  over  can  be  obtained.     As 


500,000  : 

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Weight  of  Rail -Pounds  per  Yard 

Fig.  159.     Curves  for  Finding  the  Number  of  Drivers  Needed  for  Given 
Weight  on  Driving  Wheels  and  Weight  of  Rails 

an  ordinary  value  one-fourth  {\%),  or  perhaps  nine-fortieths 
is  more  usual.  Under  unfavorable  conditions,  the  ratio  reduces 
to  one-fifth  (j^),  or  less.  The  capacity  of  the  boiler  to  make  steam 
depends  on  the  grate  area,  the  heating  surface,  and  (in  the  case  of 


264 


RAILROAD  ENGINEERING  253 

modern  heavy  freight  locomotives)  the  capacity  of  the  fireman  to 
shovel  coal. 

Experience  shows  that  an  average  fireman,  when  he  must 
maintain  the  full  power  of  the  locomotive  for  long  periods  of  time, 
can  handle  about  4000  pounds  of  coal  per  hour,  although  individual 
performances,  in  special  test  cases  and  for  short  periods  of  time, 
have  given  much  higher  values.  It  may  occasionally  be  admissible 
to  estimate  on  extra  work  up  to  5000  pounds  per  hour  for  a  short 
period,  provided  it  is  preceded  or  followed  by  easier  work.  The 
use  of  automatic  stokers  can  raise  this  hourly  consumption  very 
considerably  (say  up  to  7000  pounds)  or  up  to  the  capacity  of  the 
locomotive  to  burn  coal  properly,  whatever  it  may  be  for  the  par- 
ticular type.  There  is  of  course  no  such  limitation  in  the  use  of 
oil-burning  locomotives,  which  now  include  about  7  per  cent  of  the 
total  number  in  the  United  States.     These  are  the  exceptional  cases. 

The  power  developed  by  any  given  type  of  locomotive  depends 
largely  on  the  characteristics  of  the  coal  used.  A  British  thermal 
unit  (symbolized  as  B.t.u.)  is  the  quantity  of  heat  required  to 
raise  the  temperature  of  1  pound  of  pure  water  1°  Fahrenheit, 
when  the  water  is  at  or  near  its  maximum  density  at  39.1°  Fah- 
renheit. When  it  is  said  that  a  certain  grade  of  coal  has  14,000 
B.t.u.  it  means  that  the  heat  in  1  pound  of  that  coal  will  raise  the 
temperature  of  14,000  pounds  of  water  1°,  or,  approximately, 
100  pounds  of  water  140°.  But  although  it  only  requires  180.9 
heat  units  to  heat  water  from  32°  to  212°,  it  requires  965.7  more 
heat  units  to  change  it  from  water  at  212°  to  steam  at  212°. 
It  requires  only  53.6  more  heat  units  to  change  it  from  steam  at 
212°  to  steam  at  387.6°  or  with  a  pressure  of  200  pounds  per  square 
inch. 

A  study  of  locomotive  tests  made  at  the  St.  Louis  Exposition 
resulted  in  the  compilation  of  Table  XIX,  which  is  copied  from 
the  Proceedings  of  the  American  Railway  Engineering  Association, 
and  is  now  included  as  Table  1,  in  the  Economics  section  of  their 
Manual.  It  was  found  that  the  steam  produced  per  square  foot 
of  heating  surface  is  very  nearly  proportional  to  the  coal  burned 
per  square  foot  of  heating  surface.  The  results  are  purposely 
made  about  5  per  cent  below  the  results  obtained  in  the  St.  Louis 
tests  to  allow  for  ordinary  working  conditions. 

265 


254 


RAILROAD  ENGINEERING 


TABLE  XIX 

Average  Evaporation  in  Locomotive   Boilers   Burning  Bituminous  and 

Similar  Coals  of  Various  Qualities,  and  for  Various  Quantities 

Consumed  per  Square  Foot  of  Heating  Surface  per  Hour 

(Based  on  feed  water  at  60°  Fahrenheit,  and  boiler  pressure  200  pounds) 


Steam  per  Pound  of  Coal 

OF  Given 

Thermal  Value 

Coal  per  Square 

(lb.) 

.   Foot  of  Heating 
Surface  per  Hour 

(lb.) 

15,000 

14,000 

13,000 

12,000 

11,000 

10,000 

B.t.u. 

B.t.u. 

B.t.u. 

B.t.u. 

B.t.u. 

B.t.u. 

0.8 

7.86 

7.34 

6.81 

6.29 

5.76 

5.24 

0.9 

7.58 

7.07 

6.57 

6.06 

5.56 

5.05 

1.0 

7.31 

6.82 

6.34 

5.85 

5.36 

4.87 

1.1 

7.06 

6.59 

6.12 

5.65 

5.18 

4.71 

1.2 

6.82 

6.37 

5.91 

5.46 

5.00 

4.55 

1.3 

6.59 

6.15 

5.71 

5.27 

4.83 

4.39 

1.4 

6.37 

5.95 

5.52 

5.10 

4.67 

4.25 

1.5 

6.17 

5.76 

5.35 

4.94 

4.52 

4.11 

1.6 

5.97 

5.57 

5.18 

4.78 

4.38 

3.98 

1.7 

5.79 

5.40 

5.02 

4.63 

4.25 

3.86 

1.8 

5.61 

5.24 

4.86 

4.49 

4.12 

3.74 

1.9 

5.44 

5.08 

4.71 

4.35 

3.99 

3.63 

2.0 

5.27 

4.92 

4.57 

4.22 

3.86 

3.51 

2.1 

5.12 

4.78 

4.44 

4.10 

3.75 

3.41 

2.2 

4.97 

4.64 

4.31 

3.98 

3.64 

3.31 

2.3 

4.83 

4.51 

4.19 

3.86 

3.54 

3.22 

2.4 

4.69 

4.38 

4.07 

3.75 

3.44 

3.13 

2.5 

4.56 

4.26 

3.95 

3.65 

3.34 

3.04 

2.6 

4.44 

4.14 

3.84 

3.55 

3.25 

2.96 

2.7 

4.32 

4.03 

3.74 

3.46 

3.17 

2.88 

2.8 

4.21 

3.93 

3.64 

3.37 

3.09 

2.80 

2.9 

4.10 

3.83 

3.55 

3.28 

3.01 

2.73 

3.0 

3.99 

3.73 

3.46 

3.19 

2.93 

2.66 

The  quantity  of  steam  evaporated  for  intermediate  quantities  or  qualities  of 

coal  can  be  found  by  interpolation. 
On  bad-water  districts  deduct  the  following  from  tabular  quantities: 

For  each  ye  inch  of  accumulated  scale 10  per  cent 

For  each  grain  per  U.  S.  gallon  of  foaming  salts  in  the  average 

feed  water 1  per  cent 

190.  Power  Calculations.  Illustrative  Example.  Assume  that 
a  Mikado  locomotive,  having  a  total  heating  surface  of  2565  square 
feet  is  fired  with  coal  whose  samples  test  13,000  B.t.u.  On  the  basis 
that  a  fireman  can  handle  4000  pounds  of  coal  per  hour  and  main- 
tain such  work  throughout  his  run,  the  coal  may  be  fed  at  the  rate 


266 


RAILROAD  ENGINEERING  255 

of  --—  =  1 .56  pounds  per  hour  per  square  foot  of  heating  surface. 

ZODO 

If  the  air-dried  mine  samples  of  the  coal  tested  13,000  B.t.u.,  the 
average  run-of-car  coal  would  have  about  90  per  cent  of  this,  or 
11,700  B.t.u.  Interpolating  in  Table  XIX  for  1.56  and  11,700  we 
find  that  the  pounds  of  steam  per  pound  of  coal  would  be  4.72. 
But  since  the  locomotive  is  designed  for  use  at  175  pounds  gage 
pressure,  instead  of  200,  as  in  Table  XIX,  the  amount  of  steam 
produced  will  be  about  0.3  per  cent  more,  or  say  4.73.  The  uncer- 
tainties of  firing  are  so  great  that  such  small  corrections  may  be 
ignored.  But  considering  that  a  superheater  is  used  in  this  loco- 
motive, and  that,  with  the  usual  superheater  proportions  and 
efficiency,  0.85  pound  of  superheated  steam  may  be  considered  as 
having  the  same  volume  and  pressure  as  1  pound  of  saturated  steam, 
the  amount  of  steam  developed  by  1  pound  of  coal  is  equivalent 
to  4.73 -^  0.85  =  5.56  pounds.  Then  the  equivalent  amount  of 
steam  developed  per  hour  equals  5.56X4000  =  22,240  pounds. 

The  weight  of  steam  used  per  stroke  may  be  computed  most 
easily  by  utilizing  Table  XX,  which  is  also  taken  (but  somewhat 
amplified)  from  the  Proceedings  of  the  American  Railway  Engineering 
Association,  and  now  included  as  Table  2  in  the  Economics  section 
of  their  Manual.  The  weight  of  steam  per  foot  of  stroke  for  22 
inches  diameter  and  175  pounds  gage  pressure  is  1.106  pounds 
and  for  a  stroke  of  28  inches  (2 J  feet)  it  is  2.581  pounds.  For  a 
complete  revolution  of  the  drivers  it  is  4X2.581  =  10.324  pounds. 
Since  the  engine  can  develop  the  equivalent  of  22,240  pounds  of 
steam  per  hour  and  will  use  10.324  pounds  at  one  revolution,  it 
can  run  at  a  speed  of  22,240 -^  10.324  =  2154  revolutions  per  hour, 
or  35.9  revolutions  per  minute,  at  full  stroke  and  maintain  full 
boiler  pressure.  The  drivers  are  57  inches  in  diameter  and  there- 
fore have  a  circumference  of  (57-^  12)  X3.1416  =  14.923  feet.  The 
maximum  engine  speed  for  full  stroke  is  35.9X14.923  =  535.7  feet 
per  minute.  Multiplying  by  60  and  dividing  by  5280,  or  dividing 
by  88,  we  have  6.087  miles  per  hour  as  the  maximum  speed  at  which 
full  stroke  can  be  maintained. 

In  Table  XXI,  also  taken  from  the  proceedings  of  the  American 
Railway  Engineering  Association  and  now  included  as  Table  4  in 
the  Economics  section  of  the  Manual,  are  given  the  pounds  of  steam 

267 


256 


RAILROAD  ENGINEERING 


TABLE  XX 

Weight  of  Steam  Used  in  One  Foot  of  Stroke  in  Locomotive 

Cylinders 

(Cylinder  diameter  is  for  high-pressure  cylinders  in  compound  locomotives) 


Diameter 

Weight  op  Steam 

per  Foot  of  Stroke  for  Various  Gage  Pressures 

Cylinder 
(inches) 

220  Pounds 
per  Square 

Inch 

(lb.) 

210  Pounds 
per  Square 

Inch 

(lb.) 

200  Pounds 
per  Square 

Inch 

(lb.) 

190  Pounds 
per  Square 

Inch 
'     (lb.) 

180  Pounds 
per  Square 

Inch 

(lb.) 

170  Pounds 
per  Square 

Inch 

(lb.) 

160  Pounds 
per  Square 

Inch 

(lb.) 

12 
13 
14 
15 
15^ 

0.405 
0.475 
0.551 
0.633 
0.675 

0.389 
0.456 
0.529 
0.607 
0.649 

0.370 
0.435 
0.504 
0.579 
0.618 

0.354 
0.415 
0.482 
0.553 
0.590 

0.337 
0.396 
0.459 
0.527 
0.562 

0.321 
0.376 
0.436 
0.501 
0.535 

0.304 
0.357 
0.414 
0.476 
0.508 

16 
17 

18 

18^ 

19 

0.720 
0.812 
0.911 
0.962 
1.015 

0.691 
0.780 
0.875 
0.924 
0.975 

0.658 
0.744 
0.834 
0.881 
0.928 

0.629 
0.710 
0.796 
0.841 
0.887 

0.599 
0.676 
0.759 
0.801 
0.845 

0.570 
0.643 
0.722 
0.762 
0.804 

0.541 
0.611 
0.685 
0.724 
0.763 

191 

20 

20^ 

21 

22 

1.069 
1.125 
1.181 
1.240 
1.361 

1.027 
1.080 
1.134 
1.191 
1.307 

0.978 
1.029 
1.081 
1.134 
1.245 

0.934 
0.983 
1.032 
1.083 
1.189 

0.890 
/0.936 
0.984 
1.032 
1.133 

0.847 
0.891 
0.936 
0.982 
1.078 

0.804 
0.846 
0.888 
0.932 
1.023 

23 
24 
25 
26 
27 

1.487 
1.620 
1.758 
1.901 
2.050 

1.428 
1.555 
1.688 
1.825 
1.968 

1.361 
1.482 
1.608 
1.739 
1.875 

1.300 
1.416 
1.536 
1.661 
1.792 

1.238 
1.348 
1.462 
1.582 
1.706 

1.178 
1.283 
1.392 
1.506 
1.624 

1.118 
1.218 
1.322 
1.430 
1.542 

28 

2.204 

2.117 

2.017 

1.926 

1.835 

1.745 

1.657 

For  weight  of  steam  used  per  revolution  of  drivers  at  full  cut-off: 

Multiply  the  tabular  quantity  by  four  times  the  length  of  stroke  in  feet 
for  simple  and  four-cylinder  compounds.  For  two-cylinder  compounds 
multiply  by  two  times  the  length  of  stroke. 

per  indicated-horsepower  hour  for  simple  and  for  compound 
locomotives  for  various  velocities,  which  are  multiples  of  M,  the 
maximum  velocity  at  which  the  boiler  can  maintain  steam  at 
full  pressure.  The  table  is  computed  on  the  basis  of  200  pounds 
gage  pressure,  but  factors  are  given  for  other  pressures.  For 
example,  continuing  the  above  numerical  problem,  the  pounds  of 
steam  per  i.h.p.-hour,  for  a  simple  locomotive,  at  M  velocity,  and 
at  200  pounds  pressure,  taken  from  Table  XXI,  is  38.30;  for  175 
pounds  pressure  we  must  multiply  by  the  factor  101.7,  which  makes 


268 


RAILROAD  ENGINEERING 


257 


TABLE  XXI 

Maximum  Cut-Off  and  Pounds  of  Steam  per  I.H.P.-Hour  for 
Various  Multiples  of  M 


{M  is  maximum  velocity  in  m 

ilea  per  hour  at  full  cut-oflf, 

with  boiler  presaure 

at  200 

pounds  per  square  inch) 

Pounds  -Steam  per 

Pounds  Steam  per     1 

I.H.P.-Hour 

I.H.P. 

-Hour 

Velocity 

Cui^Ofp 
(per  cent) 

Velocity 

Cut-Opp 
(per  cent) 

Simple 

Compound 

Simple 

Compound 

l.OM 

Full 

38.30 

25.80 

2.9     M 

38.5 

24.37 

21.04 

1.1    " 

94.4 

36.46 

24.36 

3.0    " 

37.0 

24.22 

21.21 

1.2  " 

89.1 

34.89 

23.24 

3.2    " 

34.2 

24.00 

21.57 

1.3  " 

84.3 

33.56 

22.35 

3.4    " 

31.8 

23.85 

21.93 

1.4  " 

79.7 

32.41 

21.65 

3.6     " 

29.8 

23.8 

22.27 

1.5  " 

75.4 

31.40 

21.14 

3.8     " 

28.0 

23.8 

22.57 

1.6  '• 

71.4 

30.49 

20.77 

4.0    " 

26.4 

23.87 

22.85 

1.7  " 

67.7 

29.67 

20.52 

4.25  " 

24.7 

24.05 

23.22 

1.8  " 

64.3 

28.93 

20.40 

4.50  " 

23.3 

24.24 

23.56 

1.9  " 

61.0 

28.25 

20.40 

4.75  " 

22.1 

24.44 

23.85 

2.0  " 

'    58.0 

27.62 

20.40 

5.00  " 

21.1 

24.64 

24.15 

2.1  " 

55.2 

27.05 

20.40 

5.5     " 

19.5 

24.98 

24.70 

2.2  " 

52.6 

26.52 

20.40 

6.0    " 

18.4 

25.20 

2.3  " 

50.1 

26.06 

20.40 

6.5     " 

17.6 

25.45 

2.4  " 

47.8 

25.67 

20.40 

7.0     " 

17.1 

25.60 

2.5  " 

45.7 

25.32 

20.47 

7.5    " 

16.7 

25.70 

2.6  " 

43.7 

25.02 

20.60 

8.0    " 

16.4 

25.80 

2.7  " 

41.8 

24.76 

20.73 

9.0    " 

16.1 

25.90 

2.8  " 

40.1 

24.54 

20.88 

For 

steam  per  i.h.p.-hour  for  ot! 

aer  boiler  pressures 

take  the 

following 

percental 

ges  of  values  given  in  table: 

160  lb., 

103      per  cent 

180  lb.,  10] 

.  3  per  cent 

210 

lb.,  99.5  I 

3er  cent 

170  lb., 

102 . 1  per  cent 

190  lb.,  10( 

) .  6  per  cent 

200 

lb.,  99.2  1 

3er  cent 

the  quantity  38.95.  Dividing  this  into  22,240,  the  steam  produced 
per  hour,  we  have  571.0,  the  i.h.p.  at  M  velocity.  Multiplying 
this  by  33,000,  the  foot-pounds  per  minute  in  one  horsepower, 
and  dividing  by  535.7  the  velocity  in  feet  per  minute,  we  have 
35,174,  the  cylinder  tractive  power  in  pounds,  when  burning  4000 
pounds  of  coal  per  hour  and  running  at  6.087  m.p.h. 

To  obtain  the  draw-bar  pull,  we  must  deduct  the  engine  resist- 
ances which  may  be  computed  as  given  in  Table  XXII,  also  taken  from 
the  Proceedings  of  the  American  Railway  Engineering  Association 
and  now  included  as  Table  7  in  the  Economics  section  of  the  Manual. 


269 


258 


RAILROAD  ENGINEERING 


TABLE  XXII 
Locomotive  Resistances 


Total  Locomotive  Resistance  is  A-\-B+C,  in  which 

A  =  resistance  between  cylinders  and  rims  of  drivers,  and  in  pounds 

=  18.7  T-\-80  N    in  which  T  =  tons  weight  on  drivers  and 

iV  =  number  of  driving  axles. 

.6  =  resistance  of  engine  and  tender  trucks,  and  in  pounds 

=  2 . 6  jr+20  iV      in  which  T  =  tons  weight  on  engine  and  tender  trucks 

and  N  =  number  of  truck  axles. 

C  =  head-end  or  "air"  resistance,  and  in  pounds 

=  .002  V^A            in  which  7  =  velocity  in  miles  per  hour,  and 

A  =end  area  of  locomotive. 

On  the  basis  that  the  end  area  averages  125  square  feet,  the  last  formula 

becomes   C  =  0.25  V^.     The  number  of  pounds  air  resistance  for  various 

velocities  is  as  given  below. 

Ve- 

LOC- 

Resist- 

Veloc- 

Resist- 

Veloc- 

Resist- 

Veloc- 

Resist- 

Veloc- 

Resist- 

Veloc- 

Resist- 

ance 

ity 

ance 

ity 

ance 

ity 

ance 

ity 

ance 

ity 

ance 

ITY 

V 

C 

V 

C 

V 

C 

V 

c 

V 

c 

V 

C 

1 

0.25 

8 

16.00 

15 

56 

22 

121 

29 

210 

36 

324 

2 

1.00 

9 

20.25 

16 

64 

23 

132 

30 

225 

37 

342 

3 

2.25 

10 

25.00 

17 

72 

24 

144 

31 

240 

38 

361 

4 

4.00 

11 

30 

18 

81 

25 

156 

32 

256 

39 

380 

5 

6.25 

12 

36 

19 

90 

26 

169 

33 

272 

40 

'  400 

6 

9.00 

13 

42 

20 

100 

27 

182 

34 

289 

50 

625 

7 

12.25 

14 

49 

21 

110 

28 

196 

35 

306 

60 

900 

Draw-bar  pull  on  level  tangent  equals  the  cylinder  tractive  power  less 

the  sum  of  the  engine  resistances. 

At  low  speeds,  the  adhesion  of  the  drivers  should  be  considered  and 

available  draw-bar  pull  should  never  be  estimated  greater  than  30  per  cent 

of  weight  on  drivers  at  starting  with  use  of  sand,  or  25  per  cent  of  weight 

on  drivers  at  running  speeds. 

Applying  Table  XXII  to  the  numerical  problem,  item  A=(18.7X 
76.6)  +  (80X4)  =  1432  lb.  The  total  weight  of  engine  and  tender  is 
315,000  pounds;  subtracting  153,200,  the  weight  on  the  drivers,  we 
have  161,800,  or  80.9  tons,  the  weight  carried  by  the  engine  and 
tender  trucks.  Item  B  =  (2.6X80.9) +  (20X6)  =330.  Item  C  for 
velocity  ikf  is  almost  insignificant,  say  9  pounds.  The  sum  of  A,  B,  and 
C  is  1771  pounds;  subtracting  this  from  35,174  we  have  33,403  pounds, 
the  estimated  draw-bar  pull  for  that  speed  and  coal  consumption. 
To  note  the  effect  of  increasing  the  rate  of  coal  consumption, 
the  problem  may  be  again  worked  through  on  the  basis  that  the 
rate  of  coal  consumption  is  increased,  even  temporarily,  from  4000 


270 


RAILROAD  ENGINEERING  259 

pounds  to  5000  pounds  per  hour.  The  steam  developed  per  pound 
of  coal  is  reduced  from  5.56  to  4.93,  but  the  total  steam  produced 
per  hour  is  increased  from  22,240  to  24,650.  The  increased  capacity 
comes  through  a  loss  in  efficiency.  The  increased  steam  production 
raises  the  velocity  at  which  full  stroke  may  be  maintained  from 
6.087  m.p.h.  to  6.746  m.p.h.  and  the  i.h.p.  from  571.0  to  632.8. 
But  the  computed  cylinder  tractive  power  is  practically  identical, 
the  numerical  computation  of  35,174  being  only  changed  to  35,175. 
But  these  cylinder  tractive  powers  are  each  computed  for  the 
"if"  velocities,  the  maximum  velocities  at  which  full  stroke  can 
be  maintained,  and  M  is  higher  with  increased  coal  consumption. 
For  a  real  comparison,  the  figures  must  be  reduced  to  the  same 
velocity,  e.g.,  the  working  velocity  of  10  m.p.h.  10-^-6.087  =  1.643, 
the  multiple  for  the  original  problem.  For  5000  pounds  of  coal 
per  hour,  M  velocity  is  6.746  m.p.h.,  and  the  multiple  is  1.482. 
From  Table  XXIII  we  find  that  the  percentages  of  cylinder  tractive 
power  for  simple  engines  for  these  two  multiples  of  M  are  77.44 
and  81.93,  respectively.  The  higher  value  is  105.7  per  cent  of 
the  lower,  which  shows  that,  in  this  case,  adding  25  per  cent  to 
the  rate  of  coal  consumption  adds  only  5.7  per  cent  to  the  cylinder 
tractive  power  at  10  m.p.h. 

As  another  instructive  variation  of  the  same  problem,  assume 
that  the  coal  has  effective  B.t.u.  of  13,000,  instead  of  only  11,700. 
It  will  be  found  that  steam  will  be  produced  more  rapidly,  the  M 
velocity  is  6.777  m.p.h.  and  the  horsepower  at  that  velocity  is 
635.7,  but  the  cylinder  power  is  computed  to  be  35,177  pounds, 
which  is  again  almost  identical  with  the  previous  values  although 
the  M  velocity  is  still  higher.  The  multiple  for  10  m.p.h.  is  1.476 
and  by  Table  XXIII  the  per  cent  of  cylinder  tractive  power  is  82.11, 
which  is  an  increase  of  6  per  cent  over  74.44  per  cent,  showing  that 
the  increase  in  effective  B.t.u.  from  11,700  to  13,000  adds  6  per 
cent  to  the  cylinder  tractive  power  at  10  m.p.h. 

These  values  for  cylinder  power  may  again  be  checked  by  the 

simple  rule  that 

m      , .      e  (piston  diameter)^  X  effective  steam  pressure  X  stroke 

Tractive  force  =  — —. j-r-. 

diameter  oi  driver 

The    "effective    steam   pressure"    is   generally    considered   as 

85  per  cent  of  the  gage  pressure,  and  for  the  above  case  would  be 

271 


260  RAILROAD  ENGINEERING 

TABLE  XXIII* 
Per  Cent  Cylinder  Tractive  Power  for  Various  Multiples  of  M 


{M  is  maximum  velocity  in  miles  per  hour  at  which  boiler  pressure  can 

. 

be  mamtamed  with  full  cut-off) 

Veloc- 
ity 

Per  Cent 

(Com- 
pound) 

Per  Cent 
(Simple) 

Veloc- 
ity 

Per  Cent 
(Com- 
pound) 

Per 

■    Cent 
(Simple) 

Veloc- 
ity 

Per 
Cent 
(Com- 
pound) 

Per 
Cent 

(Simple) 

Start 

135.00 

106.00 

3.6  M 

32.40 

44.75 

6.4  M 

23.59 

0.5  ilf 

103.00 

103.00 

3.7  " 

31.25 

43.56 

6.5  " 

23.18 

1.0  " 

100.00 

100.00 

3.8  " 

30.10 

42.39 

6.6  " 

22.79 

1.1  " 

96.28 

95.57 

3.9  " 

29.14 

41.24 

6.7  *' 

22.42 

1.2  " 

92.55 

91.53 

4.0  " 

28.24 

40.10 

6.8  " 

22.06 

1.3  " 

88.83 

87.83 

4.1  " 

27.38 

39.00 

6.9  " 

21.71 

1.4  " 

85.12 

84.46 

4.2  " 

26.56 

37.96 

7.0  " 

21.38 

1.5  " 

81.40 

81.37 

4.3  " 

25.77 

36.97 

7.1  " 

21.06 

1.6  " 

77.68 

78.55 

4.4  " 

25.03 

36.03 

7.2  " 

20.75 

1.7  " 

73.96 

75.97 

4.5  " 

24.34 

35.13 

7.3  " 

20.45 

1.8  " 

70.25 

73.60 

4.6  " 

23.69 

34.26 

7.4  " 

20.16 

1.9  " 

66.54 

71.41 

4.7  " 

23.07 

33.41 

7.5  " 

19.88 

2.0  " 

63.21 

69.37 

4.8  " 

22.48 

32.59 

7.6  " 

19.61 

2.1  " 

60.20 

67.47 

4.9  " 

21.92 

31.82 

7.7  " 

19.34 

2.2  " 

57.48 

65.67 

5.0  " 

21.38 

31.11 

7.8  " 

19.08 

2.3  " 

54.97 

63.94 

5.1  " 

20.87 

30.42 

7.9  " 

18.82 

2.4  " 

52.68 

62.22 

5.2  " 

20.37 

29.75 

8.0  " 

18.57 

2.5  " 

50.42 

60.55 

5.3  " 

19.89 

29.10 

8.1  " 

18.33 

2.6  " 

48.16 

58.92 

5.4  " 

19.43 

28.48 

8.2  " 

18.09 

2.7  " 

46.08 

57.33 

5.5  " 

18.99 

27.87 

8.3  " 

17.86 

2.8  " 

44.10 

55.78 

5.6  " 

27.33 

8.4  " 

17.64 

2.9  " 

42.29 

54.26 

5.7  " 

26.81 

8.5  " 

17.43 

3.0  " 

40.57 

52.78 

5.8  " 

26.30 

8.6  " 

17.22 

3.1  " 

38.95 

51.33 

5.9  " 

25.81 

8.7  " 

17.01 

3.2  " 

37.42 

49.91 

6.0  " 

25.34 

8.8  " 

16.82 

3.3  " 

35.98 

48.55 

6.1  " 

24.88 

8.9  " 

16.63 

3.4  " 

34.66 

47.24 

6.2  " 

24.44 

9.0  " 

16.45 

3.5  " 

33.53 

45.97 

6.3  " 

24.01 

♦Table  5  in  Economics  Section  of  Manual  of  American  Railway  Engineering  Association. 

.85X175  =  149  pounds;  diameter  piston  =  22  inches;  stroke  =  28 
inches;  diameter  of  driver  =  57  inches.  Then  the  tractive  force 
=  35,425  pounds,  which  is  less  than  1  per  cent  in  excess  of  the  other 
values.  This  rule  is  more  simple  as  a  method  of  obtaining  merely 
the  maximum  tractive  power  at  slow  velocities,  but  the  previous 
method,  although  longer,  is  preferable,  since  it  computes  the  critical 
velocity  M,  and  also  the  tractive  force  at  higher  velocities. 

191.    Tractive  Force  at  Higher  Velocities.    At  higher  velocities 
than  My  the  cylinder  power  falls  off  quite  rapidly,  since  the  steam 


272 


RAILROAD  ENGINEERING 


261 


is  cut  off  at  part  stroke  and  is  used  expansively.  The  proper  per 
cent  of  cut-off  and  the  number  of  pounds  of  steam  per  i.h.p.  are  shown 
in  Table  XXI.  In  Table  XXI  is  given  the  per  cent  of  cylinder  tractive 
power  for  multiples  of  M,  The  table  shows,  for  example,  that,  for 
simple  engines,  the  cylinder  tractive  power  is  69.37  per  cent  of  its  value 
for  full  stroke  when  the  velocity  is  2M  and  that  when  the  velocity 
is  increased  to  5M  the  tractive  power  is  reduced  to  31.11  per  cent. 
Applying  this  to  the  above  numerical  problem,  when  M  =  6.087  m.p.h., 
the  cylinder  tractive  power  is  reduced  to  31.11  per  cent  of  35,174,  or 
10,943  pounds,  but,  since  the  velocity  is  five  times  as  great,  the 
horsepower  developed  is  31.11  per  centX5  =  1.55  times  as  great. 
It  should  be  noted  that  Table  XXIII  shows  a  slight  excess  of  tractive 
power  (6  per  cent  when  starting)  for  the  simple  engine.  This  is  due 
to  the  fact  that  with  very  low  velocities  the  cylinder  pressure  more 
nearly  equals  the  full  boiler  pressure  and  there  is  not  the  usual 
reduction  of  about  15  per  cent.  Also,  compound  locomotives 
are  operated  with  all  the  cylinders  using  full-pressure  steam,  which 
increases  their  effectiveness  at  starting  about  35  per  cent,  although 
at  some  loss  in  economy  of  steam  due  to  compounding.  But 
since  the  starting  resistances  are  so  much  greater  than  the  resist- 
ances above  5  miles  per  hour,  the  extra  assistance  is  very  timely. 
192.  Further  Power  Calculations.  Illustrative  Exainple.  Con- 
tinuing the  investigation  of  the  Mikado  locomotive  (see  article 
190),  draw  a  curve  representing  its  cylinder  tractive  power  for  all 


Velocity 

Cylinder  Tractive  Power 

Locomotive 
Resistance 

Draw-Bab 

Pull 

(multiples 
of  M) 

(miles  per 
hour) 

(per  cent) 

(pounds) 

(pounds) 

(pounds) 

0.0 

0.000 

106.00 

37,284 

1762 

35,322 

1.0 

6.087 

100.00 

32,174 

1771 

33,403 

1.2 

7.304 

91.53 

32,195 

1775 

30,420 

1.5 

9.131 

81.37 

28,621 

1783 

26,838 

2.0 

12.174 

69.37 

24,400 

1799 

22,601 

3.0 

19.261 

52.78 

18,565 

1854 

16,711 

4.0 

24.348 

40.10 

14,105 

1910 

12,195 

5.0 

30.435 

31.11 

10,943 

1993 

8,950 

6.0 

36.522 

25.34 

8,913 

2095 

6,828 

velocities  from  0  to  35  miles  per  hour.  From  the  numerical  example 
worked  out  in  article  190,  we  found  that  the  cylinder  tractive  power 
for  M  velocity  (6.087  m.p.h.)  was  35,174  pounds.  From  Table  XXIII, 


273 


262 


RAILROAD  ENGINEERING 


the  power  at  starting  is  106  per  cent  of  this,  or  37,284  pounds, 
and  the  change  in  power  is  assumed  to  vary  uniformly  in  that  range. 
By  muhiplying  35,174  by  the  various  percentages  for  the  various 
multiples  of  M,  we  have  the  tractive  power  at  the  several  velocities. 
These  values  are  plotted  in  Fig.  160.  From  Table  XXII  we  find  that 
the  locomotive  resistance  is  1762  pounds  for  the  A  and  B  resistance 
at  all  velocities  and  that  the  C  resistance  varies  from  about  9  pounds 
at  M  velocity  (6.087  m.p.h.)  to  about  333  pounds  at  6  if  velocity. 
Subtracting  these  resistances  from  the  computed  values  of  cylinder 
tractive  power,  we  have  the  "draw-bar  pull"  for  the  various  veloc- 
ities, all  as  shown  in  the  tabular  form.  These  several  values  for 
cylinder  power  and  of  draw-bar  pull  are  plotted  for  the  correspond- 


■40,000 


30.000 


£0,000  S 


10,000 


5  <  10  15  £0  S5  30  35 

Fig.  IGO,     Tractive  Power  of  Mikado  Locomotive  at  Varying  Velocities 

ing  velocities  in  Fig.  160,  giving  the  two  curves  as  shown.  The 
rapid  decrease  in  possible  draw-bar  pull  for  increase  in  velocity 
is  well  shown.  But  the  student  should  carefully  note  that  this 
curve  represents  the  limitation  of  draw-bar  pull  and  not  the  actual, 
which  may  be  considerably  less  and  which  is  measured  by  the 
resistance. 

193.  Relation  of  Boiler  Power  to  Tractive  Power.  The 
power  at  high  velocities  depends  on  the  rapid  production  of  steam, 
as  has  been  shown,  and  this  depends  on  the  area  of  the  fire  box. 
All  of  the  older  styles  of  locomotives  have  fire  boxes  limited  to  the 
width  which  can  be  properly  placed  between  the  drivers.  The 
Wootten  fire  box  was  placed  over  the  drivers,  which  made  it  incon- 


274 


RAILROAD  ENGINEERING 


263 


Mogul 

Prairie 

Cylinders,  diam.X  stroke 

20  in.X26  in. 

20  in.  X  24  in. 

Boiler  pressure 

200  pounds 

200  pounds 

Fire  box,  length  X  width 

108  in.  X  33  in. 

74  in.X66  in. 

Grate  area,  square  feet 

24.70 

34.000 

Heating  surface,  sq.  ft.,  fire  box  and  tubes 

1952.00 

2135.000 

Driving  wheels,  diameter,  inches 

51.00 

51.000 

Weight  on  driving  wheels,  pounds 

137,300.00 

122,100.000 

Weight  of  engine  alone,  pounds 

154,000.00 

153,300 .  000 

Weight  of  engine  and  tender,  pounds 

254,000.00 

253,000.000 

Assumed  B.t.u.  in  coal  used,  4000  lb.  per  hr. 

12,000.00 

12,000.000 

Coal  per  sq.  ft.  of  heating  surface  per  hour 
Pounds  steam  per  pound  coal  (Table  XIX) 
Pounds  steam  per  hour  (multiply  by  4000) 

2.05 

1.873 

4.16 

4.390 

16,640.00 

17,560.000 

Pounds  steam  per  stroke  (Table  XX) 

2.230 

2.058 

Pounds  steam  per  revolution  (multiply  by  4) 

8.920 

8.232 

Revolutions  per  hour,  at  M  velocity 

1865 . 50 

2133.500 

Revolutions  per  minute,  at  M  velocity 

31.09 

35 . 560 

Circumference  of  drivers,  linear  feet 

13.35 

13.350 

Velocity  (v),  feet  per  minute,  M  velocity 

415.05 

474.730 

Velocity  (F),  miles  per  hour,  M  velocity 

4.716 

5.394 

Horsepower  at  M  velocity  (Table  XXI) 
Cylinder  tractive  power,  pounds,  at  M  velocity 

434.40 

458.400 

31,400.00 

31,865.000 

veniently  high,  unless  the  drivers  were  objectionably  small.  Then 
the  plan  was  devised  of  placing  the  fire  box  over  a  low  pair  of  trailing 
wheels  and  behind  the  rear  pair  of  drivers.  This  plan  made  it 
possible  to  double  the  net  width  of  the  fire  box.  In  order  to  get 
essential  fire-box  area  in  the  older  styles  of  locomotives,  it  is  neces- 
sary to  lengthen  the  fire  box  until  it  is  difficult  for  the  fireman  to 
reach  and  properly  clean  and  tend  the  fire  at  the  forward  end. 
But  by  doubling  the  width,  the  fire  box  may  be  made  as  large  as 
desired  and  even  shorter  than  some  of  the  older  designs.     The 


^ 

Mogul  Locomotive 

Prairie  Locomotive 

Multiples 

OF  M 

Velocity 

Cylinder  Tractive 

Velocity 

Cylinder  Tractive 

(m.p.h.) 

Power 

(m.p.h.) 

Power 

0.0 

0.000 

33,284 

0.000 

33,778 

1.0 

4.716 

31,400 

5.394 

31,865 

1.2 

5.659 

28,740 

6.473 

29,166 

1.5 

7.074 

25,550 

8.091 

25,929 

2.0 

9.432 

21,782 

10.788 

22,105 

3.0 

14.148 

16,573 

16.182 

16,818 

4.0 

18.864 

12,591 

21.576 

12,778 

5.0 

23.580 

9,769 

26.970 

9,913 

6.0 

28.296 

7,957 

32.364 

8,075 

7.0 

33.012 

6,713 

275 


264 


RAILROAD  ENGINEERING 


increased  fire-box  area  justifies  a  greater  heating  surface  and  results 
in  a  greater  production  of  steam  per  pound  of  coal  and  a  more 
rapid  production  of  steam,  and  hence  greater  power.  The  value  of  this 
change  is  best  shown  by  a  comparison  of  two  locomotives  which 
are  very  similar  in  many  respects  except  those  due  to  the  difference 
in  fire  boxes,  etc.  The  two  locomotives  are  a  "Mogul"  (2-6-0) 
and  a  "Prairie"  (2-6-2).  The  several  characteristics,  some  of 
which  are  computed  as  in  article  192,  are  best  shown  by  tabulating 
them.     (See  top  of  p.  263.) 

Knowing  the  cylinder  tractive  power  at  M  velocity  {M  being 
somewhat  different  for  the  two  locomotives),  we  can  determine  the 


30,000 


Z  0,000 


10.000 


5  10  15  £0  £5  30  35 

Fig.  161.     Comparative  Cylinder  Tractive  Power  of  Prairie  and  Mogul  Types  of  Locomotive 


cylinder  tractive  power  for  various  multiples  of  M,  by  means  of 
Table  XXIII,  by  the  method  already  given  in  detail.  The  results 
are  tabulated  at  bottom  of  p.  263  and  are  plotted  in  Fig.  161. 

The  student  should  note  that  the  two  locomotives  are  of  almost 
the  same  weight,  have  the  same  driving-wheel  diameter,  same 
cylinder  diameter,  same  boiler  pressure,  and  are  compared  on  the 
basis  of  using  the  same  quality  of  coal.  The  Mogul  has  15,200 
pounds  extra  on  the  drivers,  which  should  apparently  give  it  advan- 
tage, but  Fig.  161  shows  that,  even  at  the  start,  the  Mogul  has 
slightly  less  tractive  power.  But  the  Prairie  fire  box  is  wider, 
although  shorter,  and  has  38  per  cent  more  area.  This  permits 
more  rapid  production  of  steam.  By  scaling  the  vertical  intervals 
between  the  two  curves  at  all  points,  it  is  found  that  for  any  veloc- 


276 


RAILROAD  ENGINEERING  265 

ities  between  5.5  and  25  miles  per  hour  the  Prairie  has  about  2000 
pounds  more  cyHnder  tractive  power.  Of  course,  the  comparison 
should  be  made  on  the  basis  of  their  relative  draw-bar  pulls,  which 
would  be  obtained  by  subtracting  the  engine  resistances,  as  given 
in  Table  XXII.  But  this  shows  that  the  engine  resistance  of  the 
Mogul  is  greater  than  that  of  the  Prairie,  which  leaves  an  even 
greater  difference  in  favor  of  the  Prairie. 

The  trailing  wheels  under  the  fire  box  also  serve  the  purpose 
of  guiding  the  driving  wheels  around  curves  when  the  locomotive 
is  running  backward  and  in  this  respect  accomplish  what  the  pilot 
truck  does  for  forw^ard  running. 

The  comparative  power  of  these  two  locomotives  may  be  shown 
by  a  numerical  example.  Assume  that  a  train  of  16  coal  cars, 
each  weighing  when  fully  loaded  70  tons,  and  a  caboose  weighing 
15  tons,  is  being  hauled  up  a  0.3-per-cent  grade  at  a  uniform  velocity 
of  about  20  miles  per  hour.    The  resistance,  by  equation  (105),  is 

i?  =  2.2X(16x70+15)  +  121.6Xl7  =  4565lb. 

The  grade  resistance  of  the  cars  is  20X0.3X1135  =  6810  pounds. 
It  is  assumed  that  all  curve  resistance  is  eliminated  by  a  sufficient 
reduction  of  grade  w^here  it  occurs  so  that  it  may  be  included  with 
the  grade  resistance.  The  velocity  being  assumed  uniform,  there 
is  no  requirement  for  energy  for  acceleration.  The  total  car  resist- 
ance is  therefore  11,375  pounds.  The  engine  resistance  is  a  function 
of  the  velocity,  but  considering  that  the  element  depending  on 
velocity  is  relatively  small,  we  will  consider  it  at  its  average  value 
for  20  miles  per  hour.  The  resistances  may  be  computed  as  1876 
and  1532  for  the  Mogul  and  Prairie  engines,  respectively,  which 
gives  13,251  and  12,907  pounds,  respectively,  for  the  total  demands 
on  cylinder  tractive  power.  These  resistances,  being  practically 
independent  of  velocity,  are  horizontal  lihes  and  are  drawn  as  shown 
in  Fig.  161.  This  indicates  that  the  limit  of  velocity  of  the  Mogul 
locomotive  with  that  train  on  a  0.3-per-cent  grade  is  less  than  18 
miles  per  hour,  while  the  Prairie  engine  could  haul  the  train  at 
over  21  miles  per  hour.  This  gain  of  3  miles  per  hour  would  have 
considerable  value  in  the  economy  of  train  operation.  Or,  it  may 
be  showTi  that  the  Prairie  engine  could  haul  19  loaded  cars  (an 
increase  of  over  18  per  cent  in  revenue  load)  and  a  caboose,  and 


277 


266 


RAILROAD  ENGINEERING 


could  haul  them  on  the  0.3-per-cent  grade  at  a  velocity  of  18  miles 
per  hour,  the  limiting  velocity  for  the  Mogul. 

The  student  should  remember  that,  as  before  intimated,  there 
are  several  elements  of  uncertainty  (such  as  the  strength  and  abihty 
of  the  fireman,  and  the  condition  of  the  track)  which  might  modify 
the  above  figures  and  make  them  unreliable  as  a  precise  measure 
of  the  real  power  of  either  locomotive,  but,  on  the  basis  of  average 
conditions,  the  figures  are  a  measure  of  the  comparative  value  of 
the  two  locomotives. 

194.  Effect  of  Grade  on  Tractive  Power.  The  effect  of 
grade  on  tractive  power  is  best  shown  by  some  numerical 
computations  whose  results  are  plotted  in  Fig.  162,  The  cylinder 
tractive  power  was  computed  for  three  engines  of  greatly  different 
total  w^eight  and  power,  but  which  had  driving-axle  loads  nearly 
identical  (about  50,750  pounds)  and  therefore,  by  the  rule  given 
in  article  188,  could  all  be  operated  on  the  same  kind  of  track. 
Using  the  Baldwin  Locomotive  Works  rule,  as  given  in  article  188, 
J  X  50,750  ^300  =  84.5,  which  means  that  the  rails  should  weigh 
at  least  85  pounds  per  yard.  Making  computations  for  these 
locomotives,  using  12,000  B.t.u.  coal,  similar  to  those  already 
detailed  in  articles  190  to  193,  it  was  found  that,  on  a  level,  the 
cylinder  tractive  powers  of  the  Pacific,  Mikado,  and  IVIallet  loco- 
motives were  29,718,  33,575,  49,095  pounds,  respectively,  when 
the  velocity  was  uniformly  10  m.p.h.  and  the  locomotives  each 
burned  4000  pounds  of  coal  per  hour.  The  several  engine 
resistances  at  10  m.p.h.  are  easily  computed  from  Table  XXII  and  are 
tabulated  below.    The  net  values,  or  the  draw-bar  pulls,  are  plotted 


Engine  Characteristics 
(At  velocity  V  =  10  m.p.h.) 

Pacific 

4-6-2 

(lb.) 

Mikado 

2-8-2 
(lb.) 

Mallet 

2-8-8-2 

(lb.) 

Cylinder  tractive  power  on  level 
Engine  resistance  on  level 
Draw-bar  pull  on  level 
Draw-bar  pull  on  3-per-cent  grade 

29,718 

2,205 

27,513 

15,213 

33,575 

2,648 

30,927 

18,207 

49,095 

4,864 

44,231 

25,631 

on  the  left-hand  vertical  line  of  Fig.  162,  and  in  each  case  are  the 
left-hand  ends  of  the  solid  lines  which  show  the  tractive  powers 
of  the  locomotives.  On  a  3-per-cent  grade  the  grade  resistances 
for  the  locomotives  equal  60  pounds  per  ton,  and  are  12,300,  12,720, 
and  18,600  pounds,  respectively.    This  reduces  the  effective  draw- 


278 


RAILROAD  ENGINEERING 


267 


bar  pull  approximately  40  per  cent  in  each  case.  Since  this  reduc- 
tion varies  uniformly  with  the  grade,  we  may  plot  the  three  values, 
15,213,  18,207,  and  25,631,  on  the  3  per  cent  vertical  line  and  draw 
straight  lines  which  represent  in  each  case  the  tractive  power  of 
the  locomotive  at  10  m.p.h.  and  on  any  grade  within  that  range. 

Assume  trains  of  cars,  all  averaging  50  tons  per  car  and  varying 
from  10  cars  weighing  500  tons  to  50  cars  w^eighing  2500  tons.  The 
resistances  at  10  m.p.h.  on  a  level  grade  are  given  by  equation  (105), 
and  may  be  plotted  on 
the  left-hand  vertical  line 
of  Fig.  162.  Grade  adds 
resistance  proportional  to 
the  grade.  For  example, 
on  a  0.7-per-cent  grade  the 
grade  resistance  per  ton 
is  14  pounds  and  for  2500 
tons  is  35,000  pounds. 
Adding  this  to  11,580,  the 
tractive  resistance,  we 
have  46,580  which  we  plot 
on  the  0.7  per  cent  ver- 
tical line.  It  is  indicated 
by  a  small  circle.  Joining 
the  two  points  gives  the 
resistance  line  for  2500 
tons  hauled  at  10  m.p.h. 
The  circles  on  the  other 
lines  indicate  similar  com- 
putations. The  intersec- 
tions of  these  resistance 
lines   with    the   lines    of 

tractive  power  indicate  the  relative  power  of  each  locomotive.  For 
example,  the  1000-ton  train  can  be  hauled  by  the  Pacific  locomotive 
at  10  m.p.h.  up  a  0.96-per-cent  grade,  but  a  Mikado  can  do  the  same 
on  a  1.1-per-cent  grade,  while  the  Mallet  can  do  it  on  a  1.52-per- 
cent grade. 

All  of  these  calculations  were  made  on  the  basis  of  burning 
4000  pounds  of   coal  per  hour,  which,  as  before  stated,  is  the 


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Curves  Showing  Effect  of  Grade  on 
Tractive  Power 


279 


268  RAILROAD  ENGINEERING 

practical  limit  of  what  an  ordinary  fireman  can  be  expected  to  do 
for  an  extended  run. 

The  description  of  the  Mallet  locomotive  (built  by  the  Baldwin 
Locomotive  Works)  stated  that  its  tractive  power  is  91,000  pounds. 
A  computation  of  its  cylinder  tractive  power  at  M  velocity,  using 
12,000  B.t.u.  coal,  shows  it  to  be  95,389  pounds.  Subtracting 
the  engine  resistance  (4843  pounds)  we  would  have  90,546  pounds, 
which  is  a  very  fair  check,  especially  as  the  Baldwin  Locomotive 
Works  method  of  calculation  is  different. 

195.  Acceleration — Speed  Curves.  The  time  required  for 
an  engine  of  given  weight  and  power  to  haul  a  train  of  known  weight 
and  resistance  over  a  track  with  known  grades  and  curvature  is 
an  important  and  necessary  matter  for  an  engineer  to  compute, 
since  the  saving  in  time  has  such  a  value  as  to  justify  constructive 
or  operating  changes  which  will  reduce  that  time.  Fig.  160  shows 
that  the  draw-bar  pull  is  very  much  greater  at  very  low  velocities 
than  at  the  moderate  speed  of  even  15  m.p.h.  In  spite  of  the 
increased  resistance  at  these  low  velocities  the  margin  of  power 
left  for  acceleration  is  also  greater  and  the  "speed  curve"  is  really 
'^  curve  and  not  a  straight  line.  Its  general  form  may  be  most 
easily  developed  by  a  numerical  example,  especially  as  each  case 
has  its  own  special  curve. 

Illustrative  Example,  The  Mikado  locomotive,  whose  char- 
acteristics have  already  been  investigated  in  article  190  et  seq., 
has  draw-bar  pulls  at  various  velocities  as  shown  in  the  tabular 
form  in  article  192,  to  which  frequent  reference  must  be  made  in 
this  demonstration.  Assume  that  this  locomotive  starts  from  rest 
on  a  0.4-per-cent  upgrade,  hauling  a  train  of  14  cars,  each  weighing 
50  tons,  and  a  caboose  weighing  10  tons.  Then  the  normal  level 
tractive  resistance,  by  equation  (105),  equals 

i?  =  (2.2x710)  +  (121.6Xl5)  =  33861b. 

The  grade  resistance  of  the  cars  will  be  20X0.4x710  =  5680  pounds. 
The  extra  starting  resistance  will  be  considered  as  6  pounds  per 
ton,  or  4260  pounds.  These  three  items  total  13,326  pounds. 
The  average  draw-bar  pull  of  the  locomotive  at  velocities  between 
zero  and  M  velocity,  which  is  6.087  m.p.h.,  is  34,362  pounds,  but 
this  must  be  diminished  in  this  case  by  20X0.4X157.5  =  1260 


280 


RAILROAD  ENGINEERING  269 

pounds  for  grade  and  by  157.5X6  =  945  pounds  for  starting  resist- 
ance, leaving  a  net  draw-bar  pull  of  32,157  pounds,  excluding  the 
force  required  for  the  acceleration  of  the  locomotive.  The  net 
force  available  for  acceleration  of  both  the  locomotive  and  the 
train  is  32,157-13,326  =  18,831  pounds,  or  prorated,  is  18,831^ 
(157.5-f-710)=21'.71  pounds  per  ton.  Transposing  equation  (104), 
with  Fi  =  0,  F2  =  6.087,  and  P  =  21.71  pounds,  we  have  *  =  (37.05-0) 
70-^21.71  =  119  feet,  the  distance  required  to  attain  a  velocity 
of  6.087  m.p.h. 

While  the  velocity  is  increasing  from  1.0  if  to  1.2  ilf,  the  mean 
draw-bar  pull  is  31,912  —  1260  =  30,652  pounds,  less  the  accelerative 
resistance  of  the  locomotive.  Subtracting  the  tractive  and  grade 
resistances  of  the  cars,  we  have  30,652  —  3386  —  5680  =  21,586 
pounds.  Note  that  there  is  no  longer  any  starting  resistance. 
The  accelerative  force  in  pounds  per  ton  is  21,586 -i- 867.5  =  24.88. 
The  distance  s  required  to  increase  the  velocity  from  6.087  m.p.h. 
to  7.304  m.p.h.,  is  (53.35 -37.05)70 -^  24.88  =  46  feet.  Similarly 
the  distances  required  to  increase  the  velocity  from  1.2  M  to  1.5  M, 
from  1.5  If  to  2  M,  etc.,  are  computed  as  in  the  accompanying 
tabular  form,  p.  270. 

The  corresponding  distances  and  velocities  have  been  plotted 
in  Fig.  163.  The  velocity  of  10  m.p.h.  is  acquired  in  a  little  over 
300  feet,  but  it  requires  nearly  1000  feet  to  acquire  a  velocity  of 
15  m.p.h.  and  about  2400  feet  to  raise  it  to  20  m.p.h.  The  force, 
in  pounds  per  ton,  available  for  acceleration  is  maximum  at  low 
velocities,  after  the  extra  starting  resistance  is  overcome.  As 
the  margin  per  ton  for  acceleration  becomes  less  and  less,  the  greater 
is  the  distance  required  to  increase  the  velocity  1  mile  per  hour — 
especially  through  the  last  increments — up  to  the  velocity  at  which 
the  net  draw-bar  pull  exactly  equals  the  total  car  resistance  and 
the  velocity  becomes  uniform.  There  is  an  approximation  in 
using  average  draw-bar  pulls  between  the  different  velocities  at 
which  the  draw-bar  pull  has  been  definitely  computed,  but  the 
computed  distances  are  practically  correct  up  to  4  if  velocity 
or  24.35  m.p.h.  But  the  computation  for  the  distance  required 
to  increase  the  velocity  from  4  M  up  to  4.58  M  is  far  less  accurate 
if  the  average  draw-bar  pull  is  used.  The  effective  pull  at  4  if 
velocity  equals  12,195  —  1260  =  10,935,  less  the  accelerative  resist- 

28X 


270 


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RAILROAD  ENGINEERING 


27i 


ance  of  the  locomotive.  The  tractive  and  grade  resistance  of  the 
cars  at  this  velocity  is  3386+5680  =  9066.  This  leaves  10,935- 
9066  =  1865  pounds  available  for  acceleration  of  both  locomotive 
and  cars.  The  reduction  in  tractive  force  between  4  If  velocity 
and  5M  velocity  (see  article  192)  is  12,195-8950  =  3245  pounds. 
By  proportionate  interpolation  we  w^ould  then  say  that  the  excess 
force  available  for  acceleration  would  be  exhausted  at  (1869-^3245) 
=  .58  of  the  interval,  or  at  a  velocity  of  4.58  M,  or  27.88  m.p.h. 
The  mean  accelerative  force  is  one-half  of  1869,  or  935  pounds, 
which  is  1.077  pounds  per  ton  of  train.    The  distance,  by  an  inver- 


^00       1000  ZOOO  *      3000.  'lOOO  •   5000 

Fig.  163.     Time  Curves  for  Mikado  Locomotive  and  Train 


6000 


sion  of  equation  (104),  is  computed  to  be  11,981  feet.  Owing  to 
the  approximate  equality  of  w^orking  force  and  resistance  and  the 
momentary  variations  in  both,  the  precise  point  where  the  accel- 
eration would  cease  and  the  velocity  would  actually  become  uniform 
would  be  very  uncertain.  Fortunately  the  inaccuracy  is  of  little  or 
no  practical  importance  and  for  the  purposes  of  our  calculations  we 
may  call  this  last  interval  11,981  feet,  assuming  that  the  grade  is  as 
long  as  17,234  feet  or  3.2  miles.  If  the  0.4-per-cent  grade  continued 
indefinitely  the  train  would  travel  at  this  uniform  velocity  as  long 
as  the  locomotive  operated  on  the  basis  assumed  for  this  problem. 
Note  that  Fig.  163  would  have  to  be  extended  to  nearly  three  times 
its  present  length  before  the  time  curve  would  reach  and  become 
tangent  to  the  *^line  of  uniform  velocity". 


272 


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1 96.  Retardation— Speed 
Curves.  When,  on  account  of 
grade  resistance,  the  total  of 
tractive  and  grade  resistance  is 
greater  than  the  draw-bar  pull, 
there  is  retardation. 

Illmtrative  Example.  Con- 
tinuing the  numerical  problem  of 
article  195,  assume  that,  while 
moving  up  the  0.4-per-cent  grade 
at  a  velocity  of  4.58  if,  or  27.88 
m.p.h.,  the  train  reaches  a  grade 
of  +1.2  per  cent.  The  grade 
resistance  of  the  cars  will  be 
20X1.2X710  =  17,040  pounds. 
The  tractive  resistance  will  be 
3386  pounds,  as  before,  making 
a  total  of  20,426  pounds.  Inter- 
polating in  the  tabular  form  in 
article  192  for  the  draw-bar 
pull  at  4.58  ilf  velocity,  we 
find  10,326;  at  4  ilf  it  is  12,195, 
and  the  mean  is  11,260;  but 
from  this  must  be  subtracted 
20X1.2X157.5  =  3780  for  grade 
resistance  of  the  locomotive, 
leaving  7480  pounds  for  the 
net  draw-bar  pull.  The  re- 
tarding force  is  20,426-7480  = 
12,946;  or  in  pounds  per  ton 
of  train,  is  12,946 -^  867.5  = 
14.92.  As  before,  using  an 
inversion  of  equation  (104), 
s  =  (777  -  593)70  ^  14.92  =  863 
feet,  the  distance  at  which 
the  velocity  would  reduce  to 
4  ilf.  As  before,  the  other 
quantities    may    be    computed 


RAILROAD  ENGINEERING  273 

and  recorded,  with  less  danger  of  confusion  and  error,  by  tabu- 
lating them,  as  given  on  p.  272. 

The  mean  velocity,  when  retarding  from  4.58  ikf  to  4.0  M, 
reduced  to  feet  per  second,  is  as  before  38.33  feet  per  second,  and 
dividing  this  into  the  distance,  863  feet,  gives  23,  the  time  in  seconds. 
The  quantities  for  the  reduction  in  velocity  from  4  ikf  to  3  If  and 
from  3M  to  2M  are  computed  similarly.  The  level  draw-bar 
pull  for  1.5  M  is  26,838  (see  article  192)  and  by  subtracting  3780, 
we  get  23,058  pounds  the  actual  net  pull  on  the  grade.  Similarly, 
the  actual  pull  at  2  M  is  18,821  pounds.    The  increase  from  18,821 

to  20,426  is  ^^  =  38  per  cent  of  the  interval  from  18,821  to  23,058 

and  38  per  cent X. 5  =  .19;  therefore,  the  actual  draw-bar  pull  just 
equals  the  resistance  at  2.0  —  .19  =  1?S1  ilf ,  or  1 1 .01  m.p.h.  The  excess 
draw-bar  pull  at  2.0  if  =  23,058 - 20,426  =  2632  pounds.  At  1 .81  M 
the  excess  is  zero  and  therefore  the  mean  excess  is  one-half  of 
2632,  or  1316.  Dividing  this  by  867.5,  we  have  1.517,  which  is 
the  value  of  P  in  equation  (104).     Then 

5  =  (148.2 -121.2)70^  1.517  =  1246  ft. 

Velocities  in  miles  per  hour  can  be  readily  converted  into 
velocities  in  feet  per  second  by  multiplying  by  1.4667.  Averaging 
the  two  velocities  at  the  beginning  and  the  end  of  each  period  gives 
the  mean  velocity;  and  dividing  each  of  these  into  the  distance  for 
that  period  gives  the  time  in  seconds. 

197.  Drifting.  The  tractive  resistance  of  the  cars  of  the 
problem  just  worked  out  is  3386  pounds;  the  locomotive  resistance 
at  20  m.p.h.  is  1862  pounds,  or  a  total  of  5248  pounds.  Variation 
in  velocity  will  affect  this  but  httle.  Dividing  by  867.5,  the  total 
weight  in  tons,  we  have  6.05  pounds,  the  resistance  per  ton,  from 
which  the  equivalent  rate  of  grade  is  6. 05 -j- 20  =  .302  per  cent. 
This  means  practically  that  when  this  train  is  running  down  a 
grade  which  is  over  .302  per  cent  it  will  run  by  gravity  and  steam 
may  be  shut  off.  If  the  grade  is  much  greater  than  .302  per  cent 
the  acceleration  on  the  downgrade  may  become  so  great,  if  the 
grade  is  very  long,  that  the  velocity  may  become  objectionably  high. 

Illustrative  Example,  Assume  that  the  Hmiting  safe  velocity 
for  freight  trains,  considering  the  condition  of  track  and  rolling 

285 


274  RAILROAD  ENGINEERING 

stock,  is  40  m.p.h.;  assume  that  the  train  we  have  been  con- 
sidering reaches  a  0.4-per-cent  downgrade  at  a  velocity  of  15  m.p.h. 
How  far  down  the  grade  will  it  run  with  steam  shut  off,  before 
the  speed  reaches  40  m.p.h.  and  brakes  must  be  applied?  There 
is  no  question  here  of  variable  tractive  power  since  the  only  motive 
power  is  gravity.  The  resistance  is  nearly  independent  of  velocity 
and  we  will  here  assume  it  to  be  so  and  utilize  Table  XVII.  At  15 
m.p.h.  the  train  has  a  velocity  head  of  7.90  feet.  At  40  m.p.h. 
the  velocity  head  is  56.19  feet.  The  train  can  therefore  drop  down 
the  grade  a  vertical  height  of  56.19-7.90  =  48.29  feet  before  the 
velocity  reaches  40  m.p.h.  On  a  0.4-per-cent  grade  the  distance 
required  for  such  a  fall  is  48.29-^.004  =  12,072  feet.  The  problem 
in  article  195  assumed  that  the  0.4-per-cent  grade  is  17,234  feet  or 
more,  and  this  shows  what  will  happen  to  the  trains  moving  in 
the  opposite  direction. 

But  it  must  not  be  thought  that  there  is  no  loss  of  energy 
during  drifting.  Even  though  no  steam  is  used  in  the  cylinders, 
some  is  frequently  wasted  at  the  safety  valve  and  more  is  used 
in  operating  brakes  and  in  maintaining  the  brake  air  reservoir 
at  full  pressure.  But  the  greatest  loss  of  heat  is  that  due  to  radia- 
tion, especially  in  winter,  in  spite  of  all  the  jacketing  devices  to 
retain  heat.  Although  the  results  of  the  numerous  tests  which 
have  been  made  are  quite  variable,  the  following  approximate 
averages  may  be  used:  the  loss  due  to  radiation  while  standing 
may  be  figured  as  120  pounds  of  coal  per  hour  per  1000  square 
feet  of  heating  surface;  while  drifting  the  loss  will  increase  to  220 
pounds  per  hour.  The  amount  of  coal  used  for  firing  up  will  be 
about  510.  This  is  based  on  the  use  of  12,000  B.t.u.  coal.  The 
better  the  coal,  the  less  will  be  used. 

Illustrative  Example.  The  Mikado  locomotive  we  have  been 
considering  has  2565  square  feet  of  heating  surface.  It  will  then 
require  about  2.565X510  =  1308  pounds  of  coal  to  fire  up.  While 
drifting  down  the  grade,  referred  to  above,  a  distance  of  12,072 
feet,  the  average  velocity  is  §(15+40)  =27.5  m.p.h.  =  40.3  ft. 
per  sec.  and  the  required  time  is  12,072-^40.3  =  300  seconds  =  5 
minutes  =  .083  hour.  The  coal  used  while  drifting  down  this  short 
run  would  be 

220 X 2.565 X. 083  =  47  lb. 


RAILROAD  ENGINEERING  275 

At  this  point  brakes  would  need  to  be  applied  and  the  time 
spent  in  drifting  beyond  this  point  must  be  computed  as  an  item 
in  the  total  time  spent  on  the  run  and  also  to  compute  the  total 
amount  of  coal  consumed  while  drifting.  Although  this  item  of 
47  pounds  is  relatively  very  small,  its  method  of  computation  is 
typical  of  the  computation  of  the  several  items  to  make  up  the 
total  of  coal  consumed  during  a  trip. 

198.  Review  of  Computed  Power  of  One  Locomotive.  It 
was  assumed  that  it  started  on  a  +0.4-per-cent  grade  with  a  load 
of  15  cars  weighing  710  tons.  After  moving  17,234  feet  (assuming 
that  the  grade  Avas  that  long)  and  doing  it  in  535  seconds,  or  8  min- 
utes 55  seconds,  the  train  acquired  a  velocity  of  27.88  m.p.h.  and  the 
power  of  the  locomotive  would  then  be  sufficient,  when  burning  4000 
pounds  of  coal  per  hour,  to  keep  it  moving  up  such  a  grade  indefinitely 
at  that  velocity.  In  case  the  grade  were  not  as  long  as  17,234 
feet,  it  w^ould  be  necessary  to  compute  the  velocity  where  the  rate 
of  grade  changed  and  make  that  the  basis  for  the  computation  on 
the  succeeding  grade.  But,  assuming  that  the  grade  were  as  long 
as  17,234  feet,  or  more,  and  that  the  velocity  of  27.88  m.p.h.  had 
been  acquired,  and  that  the  train  had  run  at  that  speed  for  some 
distance — although  this  does  not  modify  the  problem — the  train 
is  assumed  to  reach  a  still  steeper  grade,  + 1 .2  per  cent.  The  velocity 
then  begins  to  decrease  and  in  a  total  distance  of  6466  feet  and  a 
total  time  of  295  seconds,  or  4  minutes  55  seconds,  the  velocity  is 
reduced  to  11.01  m.p.h.  at  which  velocity  the  locomotive  is  able 
to  make  steam  fast  enough  to  overcome  the  higher  resistance  on 
the  steeper  grade.  From  that  point  on,  assuming  that  the  1.2-per- 
cent grade  is  longer  than  6466  feet,  the  train  would  continue  for  the 
remaining  length  of  that  grade  at  the  velocity  of  11.01  m.p.h. 

As  before  stated,  precision  in  the  above  results  depends  on 
many  factors  (such  as  B.t.u.  of  coal  used,  or  the  actual  consumption 
in  pounds  per  hour)  which  are  somewhat  variable.  Sometimes 
the  variation  of  these  factors  from  the  values  used  above  is  knowTi; 
sometimes  it  is  unknown  and  then  the  accuracy  of  the  results  is 
correspondingly  uncertain.  But  whether  accurately  known  or 
not,  w^hen  this  method  is  used,  employing  the  best  values  for  the 
factors  which  are  obtainable,  the  method  shows  a  valuable  com- 
parison of  two  proposed  alinements  or  grades.    In  such  a  com- 


287 


276  RAILROAD  ENGINEERING 

parison,  any  error  in  the  factors  will  affect  both  results  nearly,  if 
not  equally,  and  the  comparative  results  will  still  be  substantially 
correct. 

199.  Selection  of  Route.  The  preceding  articles  may  be 
utilized  in  comparing  two  routes.  If  one  of  the  lines  is  already 
in  operation,  the  engineer  has  the  great  advantage  of  being  able 
to  determine  by  test  exactly  what  results  may  be  obtained  on  that 
line  and  what  factors  should  be  used  in  computations.  It  is  then 
only  necessary  to  compute  the  quantities  for  the  proposed  new  line. 
When  both  lines  are  "on  paper"  there  is  less  certainty  as  to  the 
accuracy  of  the  results,  except  that  the  line  which  is  shown  to  be 
most  advantageous  will  probably  continue  to  be  most  advantageous 
even  if  the  uncertain  factors  used  in  the  comparison  are  somewhat 
changed.  Using  the  methods  outlined  in  articles  195  to  197,  there 
will  be  computed  the  behavior  of  an  assumed  type  of  locomotive, 
hauling  one  or  more  types  of  train  load,  and  passing  over  tracks 
having  definite  grades  and  lengths.  The  effect  of  curves  may  be 
disregarded  provided  that  the  grades  were  properly  compensated 
during  original  construction,  and  then  the  rate  of  grade  for  the 
entire  length  of  straight  and  curved  track  may  be  taken  as  the  rate 
on  the  straight  track.  If  the  rate  of  grade  is  actually  uniform, 
even  through  the  curves,  then  the  lengths  of  curved  track  must 
be  computed  separately  and  on  the  basis  of  a  rate  of  grade  equal 
to  the  actual  rate  plus  an  allowance  of  .035  per  cent  for  each  degree 
of  curve.  The  behavior  of  a  train  from  starting  to  stopping  must 
be  computed,  making  due  allowance  for  each  change  in  condition 
which  will  affect  the  hauling  power  of  the  locomotive.  The  loco- 
motive is  assumed  to  be  working  at  the  limit  of  its  steaming  capacity, 
except  when  drifting  with  steam  shut  off  on  a  downgrade,  or  when 
brakes  are  applied,  either  to  prevent  objectionably  high  velocity 
on  a  downgrade  or  to  make  a  stop.  The  action  of  brakes  during 
a  service  stop  (as  distinguished  from  an  emergency  stop)  may  be 
considered  as  a  retarding  force  varying  from  10  per  cent  to  20  per 
cent  of  the  train  weight.  Unfortunately  brake  action  is  so  variable, 
being  directly  under  the  control  of  the  locomotive  engineer  and 
varying  from  zero  to  the  full  braking  power,  that  any  computation 
of  energy  used  in  operating  them  or  of  the  effect  of  the  brakes  is 
impracticable  except  on  the  basis  of  arbitrary  assumptions  such 


RAILROAD  ENGINEERING  277 

as  the  requirement  that  the  brakes  are  used  in  such  a  way  that  a 
train  will  be  retarded  at  a  specified  rate.  The  performance  of  the 
locomotive  over  the  entire  division,  the  total  time  required,  its 
velocity  in  critical  places,  etc.,  can  be  computed.  In  articles  195 
and  196  it  was  sho^n  that  the  locomotive  considered  could  haul 
the  particular  train  considered  up  a  0.4-per-cent  grade  at  a  velocity 
of  27.88  m.p.h.  and  maintain  such  speed  indefinitely;  also  that  it 
could  haul  the  same  train  up  a  1.2-per-cent  grade  at  11.01  m.p.h. 
and  maintain  its  velocity  indefinitely.  This  of  course  means  that 
a  much  heavier  train  could  be  hauled  up  the  0.4-per-cent  grade 
and  that  a  somewhat  heavier  train  could  be  hauled  up  the  1.2-per- 
cent grade  without  being  stalled,  although  the  velocities  in  each 
case  would  be  reduced.  There  are  an  infinite  number  of  combina- 
tions but  there  are  usually  some  considerations  which  narrow  the 
choice.  Even  after  construction  is  complete  these  tables  may 
be  utilized  in  a  study  of  the  most  economical  combination  of  type 
of  locomotive  and  amount  of  train  load  for  the  track  conditions 
as  they  may  exist. 

PUSHER  GRADES 

200.  General  Principles  of  Economy.  It  frequently  happens 
that  the  natural  line  of  a  road  includes  a  few  grades  which  are  con- 
siderably higher  than  all  other  grades.  These  higher  grades  may 
be  practically  hopeless,  because  a  material  reduction  in  them  would 
cost  more  than  it  is  worth,  or  more  than  the  general  financial  con- 
dition of  the  road  can  afford.  A  common  error  is  to  consider  such 
a  grade  as  the  ruling  grade  and  then  recklessly  permit,  at  any  other 
place  on  the  road,  the  adoption  of  any  grade  less  than  this  on  the 
ground  that  it  could  never  limit  the  operation  of  trains.  But 
in  such  cases,  it  may  be  easily  practicable  to  operate  the  higher 
grades  with  a  pusher  engine  and  cut  down  all  lesser  grades  to  such 
a  rate  of  grade  that  the  "through"  engine  can  haul  as  many  cars 
on  them- as  two  engines  can  haul  on  a  pusher  grade.  The  economy 
underlying  the  method  may  be  seen  by  a  simple  illustration  which 
is  freed  from  all  details. 

Assume  that  on  a  division  100  miles  long  there  are  two  grades 
of  5  miles  each  on  which  pusher  engines  are  to  be  used;  assume 
that  the  grades  on  the  other  90  miles  are  so  low  that  one  engine 


278  RAILROAD  ENGINEERING 

may  haul  as  many  cars  on  them  as  two  engines  can  haul  on  the 
pusher  grades;  then  by  using  pusher  engines  the  weight  of  all  heavy 
trains  may  be  doubled  and  the  heavy  freight  may  be  handled  in 
half  as  many  trains.  But  this  economy  is  effected  at  the  cost 
of  operating  the  pusher  engines.  Using  single  engines  for  the 
whole  trip,  it  will  require  200  engine-miles  to  haul  a  double  load. 
But  a  single  engine  can  haul  the  double  load  over  90  miles  of  the 
run,  and  the  same  engine  with  one  pusher  can  haul  it  up  the  heavy 
grades.  Each  pusher  engine  will  travel  10  miles  on  each  grade, 
or  20  miles  for  the  two,  and  the  total  number  of  engine-miles  for 
a  double  load  will  be  120,  instead  of  200.  And  when  it  is  con- 
sidered that  the  cost  of  a  pusher  engine-mile  is  far  less  than  that 
of  an  ordinary  train-mile,  as  will  be  shown,  the  advantages  of 
the  method  are  still  more  marked. 

Of  course  the  full  economy  of  the  method  is  only  realized 
when  the  maximum  through  grade  bears  its  proper  relation  to  the 
pusher  grade.  If  the  maximum  through  grade  is  greater  than  its 
proper  corresponding  value  for  the  pusher  grade,  then  the  number 
of  cars  is  limited  by  that  through  grade  and  the  power  of  the  pusher 
engine  is  not  completely  utilized  on  the  pusher  grade.  Economy 
of  operation  requires  that  an  engine  should  work  nearly  to  the  limit 
of  its  capacity  for  as  large  a  portion  of  the  time  as  possible,  and 
therefore  when  a  heavy  engine  is  compelled  to  haul  a  light  train 
over  nine-tenths  of  the  route  in  order  that  there  shall  be  sufficient 
power  on  the  other  tenth,  where  alone  it  is  needed,  it  indicates 
a  lack  of  economy  in  the  design.  It  now  becomes  necessary  to 
develop  the  proper  relation  between  through  and  pusher  grades. 

201.  Balance  of  Grades  for  Pusher  Service.  Illustrative 
Example.  This  will  be  easiest  understood  by  a  numerical  problem. 
Suppose  that  at  two  or  three  places  on  the  line  it  seems  impracticable 
to  obtain  at  a  reasonable  expense  a  grade  less  than  2.10  per  cent 
(nearly  111  feet  per  mile).  But  since  it  seems  practicable  to  make 
a  very  much  lower  grade  elsewhere,  we  will  compute  the  corre- 
sponding through  grade  as  the  grade  to  work  for.  Assume  that 
the  through  and  pusher  engines  are  alike  and  that,  for  simplicity 
in  calculation,  they  are  of  the  Mikado  type  and  of  the  particular 
dimensions  whose  characteristics  have  already  been  developed 
in  article  190  et  seq.    The  draw-bar  pull  at   M   velocity  (6.087 

290 


RAILROAD  ENGINEERING  279 

m.p.h.)  is  33,403  pounds.  But  on  a  2.10-per-cent  grade  this  must 
be  diminished  by  20X2.10X157.5  =  6615  pounds,  the  grade  resist- 
ance. Two  such  engines  on  the  2.10-per-cent  grade  would  have 
a  total  net  draw-bar  pull  of  53,576  pounds.  Assume  that  the  trains 
to  be  hauled  are  made  up  entirely  of  coal  cars,  fully  loaded  to  100,000 
pounds,  and  weighing  40,000  pounds,  and  also  a  caboose  w^eighing 
12  tons.  On  the  basis  of  equation  (105),  the  tractive  resistance  of 
each  coal  car  is  275.6  pounds  and  that  of  the  caboose  148  pounds. 
On  the  2.10-per-cent  grade  the  total  resistance  w^ould  be  3215.6 
pounds  for  each  coal  car  and  652  pounds  for  the  caboose.  The 
net  pull  available  for  coal  cars  is  53,576  —  652  =  52,924  pounds, 
from  which  52,924-^-3215.6  =  16+,  showing  that  16  loaded  coal 
cars,  besides  the  caboose,  could  be  hauled  up  the  2.10-per-cent  grade 
by  the  two  locomotives,  and  that  there  would  be  a  considerable 
margin  of  tractive  power.  We  must  determine  the  rate  of  grade 
on  w^hich  one  locomotive,  with  a  cylinder  tractive  power  of  35,174 
pounds  at  M  velocity  (6.087  m.p.h.),  can  haul  a  load  of  157.5  tons 
(engine)  plus  16x70,  or  1120  tons  (coal  cars)  plus  12  tons  (caboose), 
or  a  total  of  1289.5  tons.  The  tractive  resistance  of  the  locomotive 
(see  article  190)  is  1771  pounds;  for  the  cars  it  is  275.6X16+148  = 
4558  pounds,  or  a  total  for  the  whole  train  of  6329  pounds.  The 
force  available  for  grade  is  35,174—6329  =  28,845  pounds,  and 
28,845 -^  1289.5  =  22.4  pounds  per  ton,  which  is  the  grade  resistance 
on  a  1.12-per-cent  grade.  The  net  result  of  the  above  calculation  is 
that  the  proposed  road  may  be  constructed  wdth  2.10-per-cent  grades 
as  pusher  grades,  provided  that  the  ruling  grade  for  single  engines 
is  kept  as  low  as  1.12  per  cent. 

Sometimes,  though  rarely,  two  pusher  engines,  and  even  three, 
may  be  used  on  a  pusher  grade.  This  might  be  found  desirable 
on  the  basis  of  a  combination  of  grades  on  each  of  which  the  resist- 
ance is  such  that  one  uniform  train  load  can  be  handled  -vsath  the 
same  facility  by  one  engine  (or  two,  or  three,  or  even  four) .  Although 
the  calculations  are  more  complex,  they  are  worked  on  precisely 
the  same  principles  as  those  used  above. 

202.  Operation  of  Pusher  Engines.  Economy  in  pusher- 
engine  work  demands  that  the  schedule  of  trains  be  so  arranged 
that  the  pusher  engine  can  be  kept  constantly  at  work.  If  there 
are  several  short  pusher  grades  separated  by  several  miles  of  level 

291 


280  RAILROAD  ENGINEERING 

track,  it  means  either  that  a  pusher  engine  must  be  assigned  to 
each  grade,  where  there  may  not  be  enough  work  to  keep  it  busy, 
and  therefore  its  daily  cost  divided  by  its  engine-mileage  is  abnor- 
mally large,  or  else  it  must  travel  uselessly  over  some  intervening 
stretches  of  level  track  in  order  to  be  at  hand  when  wanted.  Even 
the  time  table  of  the  trains  must  be  arranged  with  reference  to  the 
pusher  service  so  that  there  will  not  be  an  accumulation  of  traffic 
at  the  pusher  grades  at  certain  hours,  with  nothing  to  do  at  other 
times.  The  locating  engineer  has  no  concern  with  the  operation 
of  trains,  but  he  should  bunch  the  pusher  grades  if  possible,  even 
spending  a  little  additional  money  for  it  if  necessary. 

On  very  light-traffic  roads,  where  the  trains  are  so  few  that 
the  method  does  not  interfere  with  the  schedule,  a  pusher  grade 
may  be  operated  by  a  single  engine,  by  taking  half  of  the  train  up 
first,  leaving  it  on  a  switch,  and  then  returning  after  the  other 
half.  This  means  slow  time  (which  a  very  poor  road  can  afford); 
it  means  a  saving  of  the  cost  of  the  extra  engine,  and  also  the  com- 
paratively costly  maintenance  of  it  if  the  total  amount  of  pusher 
work  is  very  light.  Such  a  road  is  probably  not  blessed  with  an 
excess  of  traffic  except  during  a  small  part  of  the  year,  and  the 
cost  and  maintenance  of  a  useless  pusher  for  a  large  part  of  the 
year  is  thereby  saved.  But  it  should  be  noted  that  even  if  it  is 
expected  to  follow  this  policy,  it  does  not  make  the  slightest  dif- 
ference in  the  design  of  the  pusher  grades  or  in  the  ratio  of  through 
to  pusher  grades. 

Another  possible  method  of  economizing  on  pusher  service, 
especially  on  light-trafiic  roads,  where  a  pusher  grade  begins  or 
ends  near  a  station  yard  which  is  so  large  that  a  switching  engine 
is  necessary  for  at  least  part  of  the  day,  is  to  combine  the  switch- 
ing and  pusher  work.  A  little  ingenuity  in  planning  the  schedule 
will  thus  enable  the  pusher  engine  to  utilize  its  whole  time  in  useful 
work. 

203.  Length  of  Pusher  Grade.  The  true  length  which  must 
be  considered  in  the  following  calculations  is  always  somewhat 
in  excess  of  the  length  of  the  actual  grade  as  measured  on  the  profile. 
Although  it  is  sometimes  possible,  by  having  the  pusher  engine 
approach  the  train  from  behind,  to  accompUsh  its  work  without 
stopping  the  train  either  at  the  top  or  bottom  of  the  grade,  yet 

292 


RAILROAD  ENGINEERING  281 

this  requires  an  extra  length  of  track  and  considerable  extra 
mileage  on  the  part  of  the  pusher  engine.  For  passenger  service 
the  assistant  engine  is  always  placed  in  front,  and  although  it  is 
practicable  to  uncouple  the  assistant  engine  at  the  top  of  the  grade, 
run  it  ahead  at  increased  speed,  run  it  on  a  siding  and  again  clear 
the  main  track  without  stopping  the  train,  it  is  usually  necessary 
to  stop  the  train  at  the  bottom  to  couple  on.  Increased  mileage 
is  necessary  for  this.  The  stoppage  and  restarting  of  a  heavy 
train  uses  up  as  much  energy  as  would  carry  the  train  several  miles 
on  a  level  track  and  therefore  an  increased  run  by  the  pusher  engine 
is  justifiable  if  it  will  save  stopping  the  train.  A  siding  at  or  near 
the  bottom  and  top  of  the  grade  (and  also  a  telegraph  office)  is 
a  convenience  and  almost  a  necessity  for  the  quick  and  safe  opera- 
tion of  pusher  grades,  and  while  they  must  be  clear  of  the  grade  it 
is  sometimes  more  convenient  to  remove  them  some  distance  from 
the  ends  of  the  grade.  Each  case  is  a  separate  problem,  but  the 
length  to  be  used  in  the  following  calculations  must  always  be  the 
actual  run  of  the  pusher  engine,  which  will  be  somewhat  in  excess 
of  the  actual  length  of  the  pusher  grade  as  shown  on  the  profile. 
204.  Cost  of  Pusher=Engine  Service.  The  cost  depends 
partly  on  the  work  done  by  the  engine  and  partly  on  mere  time. 
The  wages  of  the  enginemen  must  be  paid  on  a  yer  diem  basis  rather 
than  on  a  mileage  basis,  and  if  the  engine  does  not  run  many  revenue 
miles,  the  cost  for  the  miles  it  does  run  is  increased.  In  view  of 
the  fact  that  the  damage  to  roadway  and  track  by  a  locomotive 
has  been  estimated  to  be  2  to  4  times  that  due  to  an  equal  weight 
of  cars,  it  is  evidently  approximately  true  that  pusher  engines, 
which  are  usually  of  the  heavy-freight  type,  should  be  charged 
about  the  same  as  the  average  charge  for  all  trains,  for  all 
the  items  of  maintenance  of  way.  According  to  Table  XVI,  this 
should  be  about  18  per  cent  of  the  average  cost  of  a  train-mile. 
Adding  the  full  percentage  for  engine  repairs,  fuel,  water,  lubricants 
and  supplies,  signaling  and  telegraph,  but  excluding  enginemen^s 
wages,  we  have,  according  to  the  figures  for  1912,  a  total  of  about 
40  per  cent  of  the  average  cost  of  a  train-mile.  To  this  must  be 
added  the  full  yer  diem  charge  for  wages  of  enginemen  and  firemen. 
In  1912,  this  averaged  for  the  whole  United  States  $5  per  day  for 
enginemen  and  S3. 02  for  firemen,  but  considering  that  there  has 


282  RAILROAD  ENGINEERING 

been  an  almost  uniform  increase  in  these  figures  from  S3. 84  and 
$2.20,  respectively,  since  1902,  their  values  during  the  next  few  years 
are  problematical  and  must  be  determined  for  each  individual 
case.  There  must  also  be  added  a  charge  for  the  capital  cost  of 
the  engine.  Since  the  cost  of  repairs  and  maintenance  has  already 
been  included,  the  initial  cost  divided  by  the  estimated  number 
of  miles  in  its  total  mileage  life  gives  a  charge  per  mile  which  covers 
the  capital  cost.  If  such  an  engine  costs  $20,000  and  its  mileage  life 
is  800,000  miles,  the  capital  cost  per  mile  is  2.5  cents.  But  since 
the  pusher  engine  must  run  2  miles  for  each  mile  of  pusher  grade, 
we  must  multiply  the  above  computed  mileage  charge  by  2  for  each 
mile  of  pusher  grade. 

Illustrative  Examdle.  A  locating  engineer  may  find  himself 
compelled  to  choose  between  two  policies,  which  may  be  illustrated 
as  follows:  Resuming  the  numerical  case  of  article  201,  assume 
that  the  engineer  finds  that  he  can  concentrate  grading  expenditures 
on  certain  parts  of  the  line  and  make  a  through  grade  with  a  max- 
imum of  1 .5  per  cent,  or  he  can  concentrate  on  other  parts  of  the 
line  and  cut  down  all  single-engine  grades  to  1.12  per  cent,  leaving 
two  grades  of  2.1  per  cent  whose  effective  pusher-grade  lengths 
(see  article  203)  are  7  and  8  miles,  respectively.  Assume  that  the 
two  methods  may  be  constructed  for  about  equal  cost.  Which 
is  preferable? 

From  the  calculations  of  article  201,  we  find  that  the  draw- 
bar pull  at  M  velocity  on  a  level  is  33,403  pounds  and  on  the  1.5- 
per-cent  grade  it  is  20X1.5X157.5  =  4725  pounds  less,  or  28,678 
pounds.  The  tractive  and  grade  resistance  of  the  caboose  is  148+ 
(20X1.5X12)  =508  pounds,  and  28,678-508  =  28,170  is  the  force 
available  for  the  coal  cars.  The  resistance  of  each  car  is  276 -|- 
(20X1.5X70)  =2376  pounds,  and  28,170^2376  =  11.8,  showing 
that  one  such  locomotive  would  be  hardly  capable,  unless  by  extra 
forcing,  to  haul  even  12  cars  up  the  ruhng  1.5-per-cent  grades. 
The  calculations  of  article  201  show  that  the  revenue  train  load 
for  the  combination  of  1.12  per  cent  through  grade  and  2.1 -per- 
cent pusher  grade  is  16  loaded  coal  cars.  Of  course  the  other  kinds 
of  traffic  should  also  be  considered;  but  if  the  passenger  traffic 
were  very  light  and  there  were  only  a  very  few  cars  per  train,  it 
might  make  no  difference,  beyond  a  comparatively  harmless  reduc- 

294 


RAILROAD  ENGINEERING  283 

tlon  in  velocity  for  a  few  minutes  each  and  at  a  few  points,  whether 
the  grade  is  1.5  per  cent  or  2.1  per  cent.  For  simphcity  we  will 
confine  the  problem  to  a  comparison  of  these  grades  on  the  basis 
of  trains  of  loaded  coal  cars.  Assume  that  the  division  is  100  miles 
long  and  that  there  is  a  traffic  against  these  grades  of  96  carloads 
of  coal  per  day.  For  simplicity  we  ignore  all  traffic  in  the  other 
direction.  The  effect  of  other  details,  for  or  against,  must  be 
computed  separately  and  independently.  With  pusher-engine 
grades  the  traffic  can  be  handled  in  6  trains;  on  the  1.5  per  cent 
through  grades,  it  will  require  8  trains  (or  9).  On  the  7-mile  pusher 
grade  there  will  be  14  pusher-engine-miles  per  trip;  on  the  other 
grade,  16.  Then  the  two  pusher  engines  must  run  84  and  96  miles, 
respectively,  per  day.  Suppose  that  the  average  cost  of  a  train- 
mile  on  that  road  is  $1.60  and  that  we  estimate  40  per  cent  of  it, 
or  64  cents,  as  the  charge  per  pusher-engine-mile  for  maintenance 
of  way,  engine  repairs,  fuel,  etc.  Suppose  that  the  pusher  engines 
cost  $16,000  and  that  the  mileage  charge  for  capital  cost  is  2  cents. 
Assume  for  wages  of  enginemen,  $5,  and  for  firemen,  $3.  Then 
the  daily  charge  for  one  engine  is 

84  (0.64-F0.02)+5.00-f3.00  =  $63.44 
and  for  the  other  engine 

96  (0.64-f0.02)-f-5.00+3.00  =  $71.36 
It  should  be  noted  that  only  the  charges  for  wages,  repairs,  and 
supplies  will  be  directly  apparent.  A  considerable  proportion 
of  the  above  cost  is  that  due  to  track  maintenance,  which  is  a  proper 
charge  but  it  may  be  forgotten.  The  proper  mileage  cost  for  through- 
freight  trains,  operated  at  the  limit  of  their  capacity,  is  evidently 
much  greater  than  that  of  the  average  train.  Assume  that  the 
cost  of  these  through-freight  trains  has  been  computed  as  $2.20 
per  mile  for  that  road,  as  against  $1.60  per  mile  for  the  average 
train.    Then  the  comparative  costs  of  the  two  systems  would  be: 

On  1.5  per  cent  through  grade:  On  1.12  per  cent  through  grade,  2.1 

8  trains  at  $2.20  per  mile,  for  per  cent  pusher  grade: 

100  miles,  per  day $1760         6  trains  at  $2.20   per  mile  for 

100  miles,  per  day $1320 

1  pusher  engine  (84  miles) 63 

1  pusher  engine  (96  miles) 71 

$1760  $1454 

295 


284  RAILROAD  ENGINEERING 

If  9  trains,  instead  of  8,  were  necessary  to  haul  the  traffic,  the 
advantage  in  favor  of  the  pusher  grade  would  be  still  greater.  On 
the  other  hand,  each  of  the  6  trains  on  the  pusher-grade  line  is 
heavier  than  one  of  the  8  trains  of  the  1 .5  per  cent  line  and  therefore 
we  might  expect  greater  injury  to  the  track  and  that  a  greater 
charge  for  track  maintenance  or  a  larger  total  expense  per  train- 
mile  would  be  charged.  But,  as  before  stated,  the  locomotive 
does  the  larger  part  of  the  damage  and  the  addition  of  cars  makes 
but  little  difference.  The  saving  of  $306  per  day,  or  $95,778  for 
313  working  days  per  year,  is  equivalent,  if  capitalized  at  5  per  cent, 
to  a  capital  expenditure  of  $1,915,560.  This  sum,  so  far  as  it  is 
accurate,  represents  the  extra  expenditure,  if  necessary,  which 
would  be  justified  to  adopt  the  pusher-grade  plan  rather  than  the 
other. 

BALANCE  OF  GRADES  FOR  UNEQUAL  TRAFFIC 

205.  Fundamental  Principles.  The  volumes  or  weights  of 
the  traffic  in  each  of  the  two  directions  on  any  road  are  usually 
quite  different  and  frequently  that  in  one  direction  is  4  or  5  times 
that  in  the  other.  The  number  of  through  engines  passing  over 
the  road  in  each  direction  each  day  is  necessarily  equal,  and, 
unless  some  engines  run  "light",  the  number  of  trains  must  be 
the  same.  The  number  of  passenger  cars  must  be  the  same,  and, 
in  the  long  run,  even  the  number  of  freight  cars  must  be  the  same. 
But  if  the  weight  of  the  freight  is  very  largely  greater  in  one  direc- 
tion than  in  the  other,  the  cars  will  run  nearly  or  quite  full  in  one 
direction  and  nearly  or  quite  empty  in  the  other  direction.  The 
lightly  loaded  trains  will  therefore  weigh  less,  and,  with  the  same 
through  engine,  can  surmount  a  steeper  grade  than  the  heavily 
loaded  train.  It  therefore  becomes  justifiable  to  introduce  a  slightly 
heavier  grade  against  the  lighter  traffic,  if  economy  of  construction 
is  thereby  obtained. 

There  are  many  roads  which  are  not  concerned  with  this  phase 
of  grade.  When  a  branch  line  runs  to  some  terminus  in  the 
mountains  so  that  practically  all  of  the  heavy  grades  are  in  one 
direction  and  there  are  no  opposing  grades  when  running  out  of 
the  mountains  (barring  a  few  harmless  sags),  there  is  no  limita- 
tion of  trains  by  grades  except  in  the  one  direction,  and  there  is 

296 


RAILROAD  ENGINEERING  285 

no  necessity  or  object  in  computing  any  balance.  But  the  through- 
trunk  Hues,  especially  those  running  east  and  west,  find  that  their 
east-bound  traffic  is  3  or  4  times  their  west-bound  traffic. 

As  a  single  instance,  from  1875  to  1880,  the  ratio  of  the  east- 
bound  ton-mileage  to  the  west-bound  on  the  Pennsylvania  railroad 
w^as  more  than  4.5  : 1.  The  difference  of  elevation  of  the  terminals 
has  little  or  no  importance  in  this  case  since  it  is  so  small  com- 
pared with  the  total  length  of  the  line,  and  since  any  possible  effect 
which  it  might  have  had  on  the  grade  is  utterly  lost  in  the  heavy 
grades  in  both  directions  when  crossing  the  mountains.  Admit- 
ting the  justification  of  a  variation  in  the  ruling  grade  in  opposite 
directions  so  as  to  produce  a  virtual  equality  in  tractive  effort,  it 
now  becomes  necessary  to  compute  the  theoretical  balance. 

206.  Computation  of  Theoretical  Balance.  In  spite  of  the 
very  evident  disparity  in  the  weight  of  the  freight  traffic  in  the 
two  directions,  there  are  some  equalizing  factors,  as  will  be  shown: 

(1)  The  locomotive  and  passenger-car  traffic  in  the  two 
directions  are  equal. 

(2)  The  passenger  traffic  in  the  two  diret^tions  will  be  equal. 
There  is  a  slight  exception  to  this  when  a  road  handles  a  consider- 
able number  of  emigrants,  but  the  effect  of  this  is  absolutely 
insignificant,  especially  in  view  of  the  further  fact  that  the  ratio  of 
dead  load  to  live  load  is  very  high  with  passenger  traffic.  Con- 
sidering that  even  50  passengers  in  a  car,  assumed  to  weigh  150 
pounds  apiece,  would  only  weigh  7500  pounds  which  is  but  one- 
sixth  of  the  45,000  pounds  which  the  car  probably  weighs,  even  a 
considerable  variation  in  passenger  traffic  each  way  would  not 
affect  the  gross  load  materially. 

(3)  Empty  cars  have  a  greater  resistance  per  ton  than  loaded 
cars.  The  difference  may  amount  to  about  4  pounds  per  ton. 
Therefore,  although  a  train  of  loaded  cars  will  require  a  greater 
gross  tractive  effort  than  an  equal  number  of  empty  cars,  the  ratio 
will  not  be  in  proportion  to  the  gross  tonnage. 

(4)  In  spite  of  the  best  care  and  regulations  on  the  part  of 
the  traffic  department,  many  freight  cars  will  run  in  the  direction 
of  the  heaviest  traffic  either  empty  or  but  partly  loaded. 

(5)  In  general  it  is  the  freight  which  has  the  greatest  bulk 
and  weight,    such    as  grain,  coal,  lumber,  ore,    etc.,  which  is 

297 


286  RAILROAD  ENGINEERING 

run  from  the  rural  districts  toward  the  cities  and  manufacturing 
districts* 

(6)  The  return  traffic,  which  consists  chiefly  of  manufactured 
products,  and  which  is  worth  as  much  as  the  other,  weighs  but  a 
imall  fraction  of  the  other. 

Illustrative  Example,  As  a  simple  numerical  illustration, 
assume  that  it  has  been  determined  that  on  a  given  east-and-west 
Hne  the  east-bound  traffic  is  3  times  the  west-bound  traffic.  Utiliz- 
ing some  of  the  data  already  worked  out  in  article  201,  assume 
that  the  ruling  grade  against  east-bound  traffic  is  1.12  per  cent,  disre- 
garding the  pusher  grade,  and  that,  as  computed,  the  Mikado  engine 
can  haul  16  loaded  cars  (50  tons  load,  20  tons  tare)  up  this  grade.  This 
car  loading  may  also  apply  to  one  type  of  box  car.  The  live  load  on 
one  train  (east-bound)  is  16X50  =  800  tons.  One-third  of  this  (for 
west-bound  traffic)  is  267  tons,  and  adding  16X20  =  320  for  tare, 
we  have  587  tons  as  the  weight  of  the  revenue  cars,  west-bound. 
The  tractive  resistance  on  a  level  of  these  16  cars  is  (2.2X587)  + 
(16X121.6)  =3247  pounds.  Adding  148  for  the  caboose  and  1771 
for  the  locomotive,  we  have  5166  as  the  total  tractive  resistance, 
and  subtracting  this  from  35,174  we  have  30,008  pounds  available 
for  grade.  The  total  train  weight  is  157.5+587+12  =  756.5  tens. 
Dividing  this  into  30,008  we  have  39.6  pounds  per  ton,  which  is 
the  equivalent  of  a  1.98-per-cent  grade.  On  the  3:1  basis,  the 
1 .98-per-cent  grade  against  west-bound  traffic  corresponds  to  the 
1.12-per-cent  grade  against  east-bound  traffic. 

207.  Estimation  of  Relative  Traffic.  The  estimation  of  the 
relative  volumes  of  traffic  on  a  road  yet  to  be  constructed  is 
usually  a  matter  of  sheer  guesswork,  except  as  it  might  be  inferred 
from  existing  roads  which  are  similar  in  character.  But  this  prob- 
lem often  forms  one  of  the  features  of  the  plans  for  the  improve- 
ment of  existing  lines  and  in  such  a  case  there  is  an  abundance  of 
existing  data.  Since  it  concerns  only  the  ruling  grades,  it  affects 
only  those  trains  which  are  affected  by  the  rate  of  the  ruling  grade. 
It  is  unfortunately  true  that  the  fluctuations  of  traffic  are  such 
that  a  ratio  which  might  have  been  perfect  at  the  time  of 
its  computation  may  become  considerably  in  error  for  a  long 
period  of  time,  if  not  permanently.  A  change  in  the  develop- 
ment  of   the   country    may    turn  an  agricultural  region  into  a 


298 


RAILROAD  ENGINEERING  287 

manufacturing  region  or  the  discovery  of  vast  deposits  of  coal 
or  ore  may  result  in  a  considerable  and  permanent  change  in  the 
flow  of  traffic. 

The  Interstate  Commerce  Commission  report  for  1911-12  gives 
the  following  as  the  chief  items  of  freight  tonnage : 

Bituminous  coal 525  million  tons 

Ores 139  million  tons 

Lumber 125  million  tons 

Anthracite  coal    119  million  tons 

Stone,  sand,  and  other  like  articles.  .  103  million  tons 

Grain 71  million  tons 

Cement,  brick,  and  lime 62  million  tons 

Coke   62  million  tons 

30  other  headings 580  million  tons 

Total         1,786  miUion  tons 

It  will  readily  be  seen  that  the  above  items  only  include  the  heavy, 
bulky  freight.  Such  an  item  of  manufacture  as  agricultural  imple- 
ments only  weighed  3,399,214  tons,  and  household  goods  and 
furniture  but  little  more.  These  figures  emphasize  the  statements 
made  above  regarding  the  relative  weights  of  various  classes  of 
traffic. 

Perhaps  the  safest  general  rule  is  to  say  that  opposite  ruling 
grades  should  be  made  equal  unless  there  is  a  definite  reason  for 
making  them  unequal.  The  reconstruction  of  the  great  trunk  lines, 
on  which  so  much  money  is  now  being  spent,  invariably  aims  at  a 
lower  grade  against  east-bound  traffic  than  that  allowed  against  the 
west-bound.  The  Canadian  Pacific  railroad  had  scarcely  been 
completed  before  there  was  a  reconstruction  with  this  end  in  view. 
While  it  is  one  of  the  most  uncertain  elements  to  calculate,  its 
justification  under  certain  conditions  is  unquestionable. 


299 


EARTHWORK 

PART  I 


INTRODUCTION 


Scope  of  Work.  This  article  is  designed  to  consider  in  detail 
the  various  kinds  of  machines  employed  in  excavation  and  their 
uses  in  the  construction  of  highways,  railroads,  reclamation  projects, 
municipal  improvements,  etc.  Each  type  of  excavator  is  discussed 
in  sufficient  detail  to  give  a  clear  idea  of  its  construction  and  field 
of  work.  The  limitations  and  cost  of  operation  of  each  machine 
for  different  kinds  of  excavation  under  average  working  conditions 
are  briefly  discussed. 

This  matter,  in  addition  to  its  uses  as  a  textbook,  is  serviceable 
as  a  brief  reference  work  for  engineers,  contractors,  and  others  inter- 
ested in  the  design  and  construction  of  earthwork. 

Fundamental  Principle.  Excavation  or  earthwork  is  one  of 
the  more  important  factors  in  nearly  all  classes  of  construction 
work.  The  fundamental  principle  of  all  earthwork  is  the  most 
efficient  use  of  the  best  machinery  to  secure  the  most  satisfactory 
results,  in  the  least  time  and  at  a  minimum  cost. 

Methods  of  Excavation.  The  proper  method  to  use  in  any 
case  depends  upon  several  factors:  magnitude  of  work,  area  over 
which  work  extends,  nature  of  soil  to  be  removed,  length  of  haul, 
cost  and  availability  of  fuel,  labor,  etc.,  location  of  work  with 
respect  to  transportation  facilities,  etc. 

When  the  job  is  small,  the  cost  of  the  installation  of  the  earth- 
handling  plant  may  be  a  large  proportion  of  the  total  cost  of  the 
work,  and  hence  it  is  necessary  to  use  an  inexpensive  equipment. 
On  a  large  job,  however,  the  cost  of  an  extensive  and  expensive 
equipment  can  be  distributed  over  a  large  amount  of  work,  and 
thus  only  slightly  affect  the  unit  cost.  Where  the  earthwork  at 
any  section  is  small  but  extends  over  a  considerable  area,  as  in  much 
highway  and  reclamation  work,  it  is  generally  most  efficiently  done 
with  scrapers,  graders,  or  some  form  of  small,  portable  excavator. 

301 


2  EARTHWORK 

Where  the  work  is  of  great  extent  at  any  section,  such  as  often 
obtains  in  the  excavation  of  deep  railroad  cuts,  large  waterways,  or 
extensive  pits,  the  use  of  the  larger  types  of  dry-land  and  floating 
excavators  affords  more  economical  and  efficient  results. 

The  light,  soft  soils  do  not  require  any  preliminary  loosening 
and  can  be  handled  by  any  form  of  hand  or  power  tool.  Dense, 
hard  soils  must  first  be  loosened  by  plowing  or  blasting,  and  the  size 
and  weight  of  the  fractured  material  usually  necessitates  its  removal 
by  some  form  of  power  excavator.  If  the  excavated  material  is  to 
be  removed  to  a  considerable  distance  and  used  for  embankments 
or  other  forms  of  fill,  some  form  of  hauling  device,  such  as  wagons, 
trains  of  cars,  or  cableway  should  be  used.  Where  the  job  is  a  long 
distance  from  a  line  of  transportation,  the  difficulty  and  cost  of 
hauling  and  the  scarcity  and  high  cost  of  fuel,  may  require  the  use 
of  small  portable  types  of  machinery. 

It  is  evident  that  the  conditions  attending  earthwork  are  so 
variable,  and  there  are  usually  so  many  unforeseen  circumstances 
which  may  affect  the  progress  of  a  job,  that  it  is  impossible  to  lay 
down  any  fixed  rules  or  specify  any  definite  methods. 

General  Details  of  Hand  Excavation.  Loosening.  When  the 
earth  is  not  to  be  excavated  with  the  larger  power  machines  and  is 
very  compact  and  hard,  it  must  first  be  loosened.  Loam,  sand,  and 
soft  clay  can  be  excavated  with  the  smaller  types  of  machines  with- 
out preliminary  loosening. 

The  tools  and  methods  to  be  used  depend  upon  the  magnitude 
and  shape  of  the  work,  the  character  of  the  soil,  the  depth  of  cut, 
etc.  The  tools  used  for  loosening  are  the  mattock,  the  pick,  and  the 
plow. 

The  mattock  is  a  long-handled  tool  resembUng  a  pickax,  but 
having  blades  instead  of  points;  the  blades  being  set  at  right  angles 
to  each  other.  This  tool  should  be  used  for  cleaving,  and  trimming 
the  surface.  The  pick  is  made  either  with  two  points  or  with  one 
point  and  a  chisel-shaped  end.  Its  use  is  adapted  largely  to  very 
dense,  hard  soils  such  as  cemented  gravel,  hardpan,  and  loose  rock, 
and  in  restricted  places  such  as  narrow  trenches,  pits,  and  corners, 
which  cannot  be  reached  by  the  plow  or  power  excavators.  The 
amount  which  can  be  loosened  by  a  laborer  in  a  10-hour  day  varies 
with  the  skill  and  industry  of  the  man,  the  supervision,  character  of 


EARTHWORK  3 

the  soil,  working  space,  etc.,  but  will  average  about  12  cubic  yards 
for  hardpan  and  cemented  gravel  and  20  cubic  yards  for  dense  clay. 

The  plow  is  the  most  generally  used  form  of  tool  for  loosening 
hard,  compact  soils  and  is  made  in  several  styles  for  different  classes 
of  w^ork.  The  ordinary  mold-board  type  of  plow  used  on  the  farm, 
is  adaptable  for  general  use  in  ordinary  soils,  but  for  very  hard 
materials  a  heavy  wedge-pointed  plow,  known  as  the  pavement 
plow,  should  be  used.    A  heavy  pavement  plow  is  shown  in  Fig.  1. 

A  2-horse  plow  with  a  driver  will  loosen  about  400  cubic  yards 
of  average  soil  per  10-hour  day.  If  the  material  is  a  dense  clay  or 
gumbo,  the  daily  output  w4th  a  4-horse  team  and  three  men  will  be 
from  150  to  200  cubic  yards.  If  it  is  assumed  that  the  labor  cost 
for  team  and  plow  is  $3.50,  and  for  the  plow  holder  is  $1.50  per  10- 


Fig.  1.     Typical  Hardpan  or  Rooter  Plow 
Courtesy  Western  Wheeled  Scraper  Company,  Aurora,  Illinois 

hom*  day,  the  cost  of  loosening  loam  and  clay  will  be  about  1|  cents 
per  cubic  yard,  and  for  dense,  hard  clay  will  be  about  4  cents  per 
cubic  yard. 

Hand  Shoveling.  Shovels  are  made  with  either  round  or 
square-pointed  blades  and  long  or  short  wooden  handles.  The 
round-pointed  shovel  is  more  efficient  in  the  removal  of  stiff,  dense 
soils,  and  should  be  used  with  a  short  D-handle.  The  long-handled, 
round-pointed  shovel  is  the  more  economical  for  average  soils  and 
should  be  used  where  the  men  are  not  cramped  for  working  space. 
A  laborer  can  shovel  loose  material  and  elevate  it  into  a  wagon  or 
upon  a  platform  at  the  rate  of  from  15  cubic  yards  to  10  cubic  yards 
per  10-hour  day  for  elevations  of  from  3  feet  to  6  feet,  respectively. 
In  stiff  clay  or  hard  gravel,  these  quantities  will  be  reduced  to  from 
8  cubic  yards  to  5  cubic  yards,  respectively. 


303 


4  EARTHWORK 

DRAG  AND  WHEEL  SCRAPERS 

Drag  Scraper.  The  drag,  slip,  or  scoop  scraper  is  a  steel  scoop 
or  pan  with  a  rounded  back  and  curved  bottom.  The  latter  is 
either  provided  with  runners  or  reinforced  mth  a  thin  steel  plate, 

known  as  a  "double  bot- 
tom". Wooden  handles  are 
attached  to  either  side  near 
the  rear  of  the  pan  and  are 
used  by  the  operator  in 
loading  and  dumping  it.  A 
heavy  bail  with  a  swivel 
eye  is  used  for  attaching  a 
team  of  horses.  The  fol- 
lowing tabulation  gives  the 
description  and  cost  of  the 
various  sizes  of  ordinary 
drag  scrapers. 


Fig.  2.     Drag  Scraper 

Courtesy  Western  Wheeled  Scraper  Company, 

Aurora,  Illinois 


Drag  Scraper 


No. 

Description 

Capacity 
(cu.  ft.) 

Weight 
(lb.) 

Cost 

1 
2 
3 
1 

2 

With  runners 
With  runners 
With  runners 
With  double  bottom 
With  double  bottom 

7 
5 

5 

95 
85 
75 
100 
90 

$4.50 
4.25 
4.00 
5.00 
4.75 

The  loading  position  of  a  drag  scraper  is  shown  in  Fig.  2. 

The  material  can  be  excavated  directly  with  the  scraper  where 
the  soil  is  a  loose  loam,  clay,  or  sand.  For  harder  and  more  compact 
soils,  the  material  must  first  be  loosened  by  a  plow.  The  actual 
capacities  (place  measurement)  of  a  scraper  will  average  about  one- 
half  the  rated  capacities  given  in  the  tabulation.  The  pan  is  rarely 
filled  and  the  material  is  loose. 

Drag  scrapers  are  efficient  for  hauls  up  to  100  feet,  and  can  be 
satisfactorily  used  up  to  200-foot  hauls.  A  2-horse  team  and  scraper 
can  move,  in  a  10-hour  working  day,  the  following  average  quanti- 
ties of  loose  material. 


304 


EARTHWORK 
Drag  Scraper  Service 


Length  of  Haul 

Output  per  Day 

(ft.) 

(cu.  yd.) 

25 

70 

50 

60 

100 

50 

150 

40 

200 

35 

The  following  cost  of  excavation  is  approximately  correct  under 
average  working  conditions.  The  figures  stated  include  plowing, 
loading,  hauling,  dumping,  spreading,  supervision,  and  repairs. 

Cost  of  Excavation 


Length  of  Haul  (ft.) 

50 

100 

150 

200 

Character  of  Soil: 

Average 

Hard 

$0.10 
0.13 

$0.12 
0.15 

$0.14 
0.17 

$0.16 
0.19 

Field  of  Usefulness.  The  drag  scraper  has  been  used  univer- 
sally in  this  country  during  the  last  quarter  of  a  century  in  the  con- 
struction of  roads,  railroad  embankments,  and  levees.  In  recent 
years  its  field  of  usefulness  has  been  extended  to  the  construction 
of  broad,  shallow  canals  and  ditches,  the  excavation  of  foundations 
for  various  structures  and  of  areas  for  reservoirs,  borrow  pits,  etc. 
The  slip  scraper  is  efficient  for  hauls  under  200  feet  and  for  work 
whose  magnitude  is  approximately  less  than  50,000  cubic  yards. 

Fresno  Scraper.  The  Fresno  or  Buck  scraper  is  a  long,  narrow 
pan  with  a  rounded  back.  It  is  especially  adapted  to  the  removal 
of  a  wide  strip  of  soil  in  thin  layers,  and  to  spreading  it  out  over  a 
road  grade  or  spoil  bank.  The  following  tabulation  gives  the 
various  sizes,  capacities,  weights,  and  costs  of  a  typical  make. 


Fresno  Scraper 

No. 

Description 

Capacity 
(cu.  ft.) 

Weight 

(lb.) 

Cost 

1 
2 
3 

5  -foot  cutting  edge 
4  -foot  cutting  edge 
3|-foot  cutting  edge 

18 
14 
12 

316 
260 
245 

$27.00 
25.50 
22.50 

305 


6 


EARTHWORK 


The  Fresno  scraper  is  generally  operated  in  groups  of  from  2  to 
10,  with  a  driver  for  each  scraper,  and  one  man  to  load  for  the  group. 

The  economical  haul  of  this  type 
of  scraper  is  about  300  feet.  A 
4-horse  team  is  ordinarily  used 
and  furnishes  a  sufficient  load- 
ing power  for  ordinary  soils.  A 
view  of  the  Fresno  scraper  in  its 
loading  position  is  shown  in 
Fig.  3. 

Field  of  Usefulness.  The 
Fresno  scraper  is  most  efficient  in  the  construction  of  ditches  and 
embankments  where  the  soil  is  ordinary  loam,  clay,  or  sand,  and  is 
free  from  large  stones  and  stumps.  For  side-hill  work  this  scraper 
is  especially  efficient  in  transporting  earth,  as  it  will  often  push 
ahead  of  itself  a  huge  mass  of  loose  material. 

In  the  construction  of  ditches  or  canals  in  a  sandy-clay  soil 
under  average  working  conditions,  the  Fresno  scraper  will  remove 
50  to  100  cubic  yards  with  a  haul  of  70  to  150  feet,  during  a  10-hour 
working  day,  at  a  cost  of  from  8  cents  to  10  cents  per  cubic  yard. 


Fig.  3.     "Western"  Type  of  Fresno  Scraper 


Fig.  4.     Typical  Wheeled  Scraper 
Courtesy  Western  Wheeled  Scraper  Company,  Aurora,  Illinois 

Two=Wheel  Scraper.  The  wheel  scraper  consists  of  a  steel  box 
mounted  on  a  single  pair  of  wheels  and  equipped  with  levers  for  the 
raising,  lowering,  and  dumping  of  the  pan,  while  the  team  is  in 
motion.    An  automatic  end  gate  is  sometimes  used  for  the  enclosure 


806 


EARTHWORK  7 

of  the  pan  and  to  prevent  loss  of  material  on  steep  slopes.  The 
following  tabulation  gives  the  various  sizes,  capacities,  weights,  and 
costs  of  a  typical  make. 

Two-Wheel  Scraper 


No. 

Capacity 
(cu.  ft.) 

Weight 
(lb.) 

Cost 

1 
2 

21 
3 

10 
13 
15 
17 

450 
690 
700 
850 

$45.00 
52.50 
57.00 
60.00 

The  loading  position  of  a  wheel  scraper  is  shown  in  Fig.  4. 

The  2-wheel  scraper  is  an  efficient  earth  mover  for  hauls  up 
to  800  feet,  and  more  efficient  than  the  drag  scraper  for  hauls  over 
200  feet.  A  2-horse  team  and  scraper  can  move,  in  a  10-hour  work- 
ing day,  the  following  average  quantities  of  loose  material. 

Two=Wheel  Scraper  Service 


Length  op 

Output  peb 

Haul 

Day 

(ft.) 

(cu.  yd.) 

100 

60 

200 

50 

300 

40 

400 

30 

The  following  cost  of  excavation  is  approximately  correct 
under  average  working  conditions.  The  figures  stated  in  the  tabu- 
lation include  plowing,  loading,  hauling,  dumping,  spreading,  super- 
vision, and  repairs. 

Cost  of  Excavation 


Length  op  Haul  (ft.) 

100 

200 

300         400 

500 

600 

700 

800 

Character  of  Soil: 

Average 

Hard 

$0.10 
0.13 

$0.12 
0.15 

$0.14 
0.17 

$0.16 
0.19 

$0.18 
0.21 

$0.20 
0.23 

$0.22 
0.25 

$0.24 
0.27 

Field    of    Usefulness.    The    2-wheel    scraper    has    about    the 
same  scope  as  the  drag  scraper;  being  limited  to  shallow  excavation 


307 


8  EARTHWORK 

where  the  magnitude  of  the  job  does  not  exceed  50,000  cubic 
yards.  The  economical  operation  of  the  2-wheel  scraper  is  within 
hauls  of  from  200  feet  to  800  feet. 

Like  its  prototype,  the  drag  scraper,  the  wheel  scraper  is  most 
serviceable  in  the  construction  of  small  railroad  embankments  and 
levees,  where  the  continual  movement  of  the  teams  over  the  fill  is  a 
valuable  factor  in  the  compacting  of  the  material.  On  short  hauls 
of  from  200  feet  to  400  feet,  where  the  soil  is  an  average  loam, 
clay,  or  sand,  and  the  cut  is  shallow,  the  2-wheel  scraper  can  be 
economically  used  on  highway,  railroad,  and  ditch  construction, 
and  in  the  excavation  of  cellars,  reservoirs,  pits,  etc. 

Four=Wheel  Scraper.  This  machine  is  made  in  two  sizes,  with 
pan  of  ^-  and  1-yard  capacities.  The  pan  of  the  scraper  is  hung  by 
chains,  on  a  steel  frame  which  is  supported  on  two  2-wheel  trucks. 
The  front  wheels  are  underhung  so  that  short  and  sharp  turns  may 
be  made.  The  pan  in  the  loadhig  position  has  the  cutting  edge 
touching  the  surface.  The  pan  is  operated  by  4  levers,  which  are 
all  within  easy  reach  of  the  driver  or  operator  who  is  seated  just 
behind  the  rear  truck,  and  on  the  right-hand  side  of  the  machine. 
The  motive  power  is  furnished  by  a  team  of  horses.  A  snatch  team 
of  two  or  more  animals,  or  a  traction  engine,  is  used  in  loading. 

The  pan,  when  filled,  is  automatically  elevated  by  a  sprocket 
chain  while  the  machine  is  in  motion.  The  load  is  dumped  through 
a  lever-operated  gate  in  the  rear  of  the  pan  while  the  scraper  moves 
over  the  dump.  Fig.  5  shows  several  4-wheel  scrapers  on  the 
construction  of  reservoir  embankments  and  irrigation  canals. 

The  4-wheel  scraper  is  about  100  per  cent  more  efficient  than 
the  2-wheel  scraper  for  200-foot  hauls,  and  this  greater  efficiency 
increases  with  the  length  of  haul.  It  can  be  economically  used  for 
hauls  up  to  2000  feet. 

Field  of  Usefulness,  The  4-wheel  scraper  is  well  adapted  to 
highway,  railroad,  and  ditch  construction,  and  in  any  shallow  excava- 
tion where  the  quantity  of  material  to  be  moved  is  less  than  50,000 
cubic  yards,  and  soil  conditions  do  not  require  the  use  of  a  power 
excavator. 

On  highway,  railroad,  and  reclamation  work,  where  the  cut 
varies  from  1  foot  to  3  feet,  and  the  haul  is  from  400  feet  to  1000 
feet,  7  to  10  scrapers,  loaded  by  1  traction  engine,  can  excavate 

308 


EARTHWORK 


309 


10  EARTHWORK 

from  500  to  800  cubic  yards  of  clay  and  loam  at  an  average  cost  of 
from  10  cents  to  15  cents  per  cubic  yard. 

GRADERS 

Two=Wheel  Blade  Grader.  The  simplest  form  of  scraping 
grader  is  the  2-wheel  grader,  which  consists  of  a  2-wheel  truck 
carrying  an  adjustable  blade.  The  blade  is  controlled  by  two 
levers,  which  are  operated  by  the  driver  who  is  seated  at  the  rear  of 
the  machine.  The  wheels  are  flanged  to  prevent  lateral  slipping  of 
the  machine  on  an  inclined  surface.     The  machine  weighs  500 


Fig.  6.     Two-Wheel  Grader 
Courtesy  of  Baker  Manufacturing  Company 

pounds  and  costs  $125,  f.  o.  b.  factory.  A  detailed  view  of  a 
2-wheel  grader  is  given  in  Fig.  6. 

Field  of  Usefulness.  The  2-wheel  grader  is  especially  adapted 
to  the  excavation  of  small  road  and  drainage  ditches.  In  soft  soil, 
the  average  capacity  of  a  machine  operated  by  2  horses  and  a  driver, 
is  J  mile  of  V-shaped  ditch,  24  inches  deep,  in  a  10-hour  day. 

Four=Wheel  Blade  Grader.  The  4-wheel  grader  consists 
essentially  of  an  adjustable  scraper  blade,  which  is  carried  by  a 
frame  supported  on  4  wheels.  The  blade  is  controlled  by  levers,  or 
chains,  and  can  be  set  at  any  angle  with  the  direction  of  draft,  raised 
or  lowered  to  any  height  or  angle,  and  tilted  to  the  front  or  rear. 
The  tractive  power  may  be  horses  or  a  traction  engine;  the  latter 


SIO 


EARTHWORK 


11 


being  more  economical  in  stiff  or  hard  soils.  The  rear  axle  is  usually 
made  telescoping,  so  that  the  frame  of  the  machine  may  be  shifted 
to  either  side.  This  allows  one  rear  wheel  to  bear  against  the  side 
of  the  ditch  when  making  a  cut. 

The  ordinary  4-wheel  road   grader  is  made  in  various  forms 


Fig.  7.     Large  Size  Road  Grader 
Courtesy  of  F.  C.  Austin  Drainage  Excavator  Company,  Chicago 

and  sizes.    The  following  tabulation  gives  the  sizes,  weights,  and 
costs  of  a  typical  make. 

Four-Wheel  Blade  Grader 


Cost 
(f.  o.  b. 
factory) 


Description 

Blade 

Light 
Standard 
Large 
Very  large 

15  in.  X    6  ft. 
15  in.  X    7  ft. 
15  in.  X    7  ft. 
18  in.  X  12  ft. 

$135 
225 
250 
300 


A  large-size  blade  grader  on  road  construction  is  shown  in 
Fig.  7. 

Reclamation  Grader.  A  scraping  grader,  which  is  especially 
designed  for  the  construction  of  ditches  is  shown  in  Fig.  8.  In  this 
case,  2  graders,  drawn  by  a  traction  engine,  are  being  used  in  coordi- 
nation on  road  construction.  This  machine  has  a  much  greater 
latitude  in  the  vertical  adjustment  of  blade  and  in  the  lateral  or 


311 


12 


EARTHWORK 


oblique  motion  of  the  wheels  of  both  trucks.  The  inclined  wheels 
allow  for  excavation  on  slopes  and  offer  resistance  to  the  lateral 
thrust  of  the  earth.  This  grader  is  hauled  by  12  horses,  or  by  a 
traction  engine,  weighs  3800  pounds,  and  costs  $750,  f.  o.  b.  factory. 
Method  of  Operation.  The  4-wheel  blade  grader  is  operated 
so  as  to  excavate  a  continuous  slice  of  earth  from  one  side  of  a  cut 
and  move  it  laterally  and  gradually  by  making  several  trips  or 
rounds  of  the  machine.     In  road  construction,  the  various  steps  are 


•Fig. 


Scraping  Grader  Especially  Designed  for  Constructing  Ditches 


shown  in  Fig.  9.  The  grader  starts  at  the  side  of  the  road  with  the 
blade  elevated  so  that  the  point  will  act  as  a  plow.  On  the  second 
round,  with  the  front  and  rear  wheels  in  line,  the  blade  is  lowered 
and  follows  the  furrow  made  on  the  first  round.  The  third  round  is 
made  with  rear  wheels  near  center  of  road  and  the  blade  more  nearly 
horizontal  and  swung  around  so  as  to  push  the  earth  towards  the 
center  of  the  road.  The  final  round  is  made  with  the  wheels  in 
line  and  the  blade  nearly  at  right  angles  to  the  draft  and  so  hung  as 
to  level  off  the  material. 


312 


EARTHWORK 


13 


Field  of  Usefulness.  The  road  grader  can  be  used  efficiently  in 
the  construction  of  roads  and  ditches.  The  2-wheel  grader  is 
suitable  for  the  grading  up  of  roads  and  the  excavation  of  small 
ditches  where  the  soil  is  dry  and  not  very  hard.  The  4-wheel 
grader  is  especially  serviceable  in  road  construction  and  the  excava- 
tion of  the  upper  sections  of  large  ditches  or  canals.  The  type  of 
4-wheel  grader  known  as  the  * 'reclamation  grader"  is  especially 
adapted  to  side-hill  work  and  the  excavation  of  ditches.  The  ordi- 
nary blade  grader  of  any  type  is  not  serviceable  in  the  excavation  of 
wet,  soft,  or  very  hard  soils. 


Fig.  9.     Diagram  Showing  Four  Stages  of  Road  Construction 

The  traction  engine  is  the  most  economical  and  efficient  form  of 
tractive  powder,  and  can  be  used  to  haul  graders  in  pairs,  thus  effect- 
ing a  considerable  economy  of  time  and  labor.  Fig.  8. 

Cost  of  Operation,  The  standard  size  of  4-wheel  blade 
grader  will  require  the  services  of  5  horses,  or  of  a  traction  engine, 
and  of  2  men,  at  an  operating  cost  of  about  $12  per  day.  In  the 
excavation  of  ditches  and  the  grading  up  of  roads,  for  loam  and 
clay,  with  light  grades,  the  output  will  average  about  1000  cubic 
yards  or  about  18,000  square  yards  of  road  surface  covered  during 
a  10-hour  day.    The  average  cost  of  road  construction  will  vary 


313 


14 


EARTHWORK 


from  1|  cents  to  2^  cents  per  cubic  yard,  depending  on  soil,  width 
of  road,  size  of  scraper,  depth  of  cut,  etc. 

Elevating  Grader.    The  elevating  grader  consists  of  a  frame 


Fig.  10.     Elevating  Grader  Mold-Board  Plow 
Courtesy  of  Western  Wheeled  Scraper  Company,  Aurora,  Illinois 

supported  on  2  pairs  of  wheels.  From  the  frame  is  suspended  a 
plow  and  a  transverse  inclined  frame,  which  carries  a  wide,  travehng, 
endless  belt.    The  plow  may  be  either  of  the  disc^^or  mold-board 


Fig.  11.    Elevating  Grader  with  Disc  Plow 
Courtesy  of  Western  Wheeled  Scraper  Company,  Aurora,  Illinois 

type.  The  elevator  frame  is  adjustable  both  as  to  length  and 
incUnation.  The  plow  is  adjustable  on  an  independent  frame  and 
loosens  the  soil  which  is  caught  upon  the  lower  end  of  the  inclined 


314 


EARTHWORK 


15 


elevator.  An  elevating  grader  with  a  moldb-oard  plow  is  shown  in 
Fig.  10,  and  one  equipped  with  a  disc  plow  in  Fig.  11.  The  moving 
belt  carries  the  material  to  the  outer  and  upper  end  of  the  elevator, 
where  it  falls  upon  the  spoil  bank  or  into  wagons.  The  elevator 
side  of  a  grader  is  showTi  in  Fig.  12. 

The  elevating  grader  is  generally  made  in  3  sizes,  which  are 
described  in  the  following  tabulation. 

Elevating  Grader 


SiZK 

Conveying 
Radius 

(ft.) 

Weight 
(lb.) 

Cost 
(f.  o.  b. 
Factor^') 

Small 

Standard 

Large 

10  to  18 
15  to  21 
18  to  30 

8600 

^400 

12000 

$  950 
1000 
1400 

The  motive  power  is  ordinarily  furnished  by  10  to  16  head  of 
horses  or  mules,  depending  on  the  size  of  the  machine  and  the  char- 


,,ag^ 

^^ 

^^^^5^8S85*»,jj;i.j''*-K 

piulb:^-'^'^if)^^f^^H 

w^-^^^^ 

Fig.  12.     Elevator  Side  of  Elevating  Grader 
Courtesy  of  Western  Wheeled  Scraper  Company,  Aurora,  Illinois 

acter  of  the  soil.  For  large  jobs  and  in  hard  soils,  the  traction  engine 
is  the  more  economical  form  of  tractive  power.  In  the  larger  sizes 
of  machines,  the  elevating  belt  is  often  propelled  by  a  5-  to  7-h.  p. 
gasoline  engine,  mounted  on  the  rear  of  the  frame. 

Cost  of  Operation.  The  standard  size  of  elevating  grader  wdll 
require  12  horses,  or  a  20-h.  p.  traction  engine,  2  drivers,  and  an 
operator,  for  its  efficient  operation.  The  capacity  of  the  machine, 
working  in  clay,  will  average  about  800  cubic  yards  for  a  10-hour 


315 


16 


EARTHWORK 


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316 


EARTHWORK  17 

working  day.  For  a  haul  of  about  300  feet,  five  IJ-yard  dump 
wagons  will  be  necessary  to  keep  one  grader  busy.  The  cost  of 
operation  will  vary  from  10  cents  to  15  cents  per  cubic  yard,  depend- 
ing on  soil  and  labor  conditions,  the  kind  of  tractive  power  used, 
method  of  disposal  of  excavated  material,  etc. 

Field  of  Usefulness.  The  elevating  grader  is  a  time-honored 
and  efficient  type  of  excavator  in  road  construction.  It  is  more 
economical  than  the  blade  grader  as  the  excavated  material  is  trans- 
ported in  one  operation  by  the  former  machine,  as  compared  with 
several  trips  required  of  the  latter.  The  blade  grader,  however, 
must  be  used  to  finish  up  the  road  surface  behind  the  elevating 
grader.  The  blade  grader  must  also  be  used  in  the  grading  up  of 
old  roads,  where  the  side  ditches  are  narrow  or  deep. 

The  soil  conditions  must  be  favorable  for  the  efficient  operation 
of  the  elevating  grader.  Very  loose  and  light  soils  cannot  be  raised 
by  the  plow,  and  wet,  sticky  soils  work  with  great  difficulty.  The 
presence  of  roots,  stumps,  boulders,  and  similar  obstructions  in  the 
soil  reirder  the  operation  of  the  grader  very  unsatisfactory. 

In  recent  years  the  elevating  grader  has  been  used  with  con- 
siderable success  in  the  West,  in  the  excavation  of  large  ditches  and 
canals,  especially  on  irrigation  projects.  This  type  of  excavator 
cannot  be  used  to  advantage  on  a  ditch  having  a  bottom  width  of 
less  than  10  feet.  A  large  grader  excavating  an  irrigation  canal  is 
shown  in  Fig.  13. 

On  railroad  work,  the  grader  is  not  well  adapted  to  the  making 
of  cuts.  Usually  there  is  not  sufficient  room  in  a  single-track  cut 
for  the  operation  of  the  grader  with  wagons,  and  unless  the  width 
of  cut  is  35  feet  or  over  there  is  insufficient  space  for  the  wagons  to 
pass  the  machine,  and  much  of  the  excavated  material  has  to  be 
rehandled. 

POWER  SHOVELS 

Classification.  Power  shovels  may  be  classified  as  to  the  kind 
of  power  used.  Formerly  all  shovels  were  operated  by  steam  power, 
but  during  the  last  decade,  wdth  the  universal  and  economical  use 
of  electric  power,  the  electric  motor  has  in  many  cases  replaced  the 
steam  engine  as  the  prime  mover  in  their  operation.  As  the  steam- 
operated  shovel  is  the  most  generally  used,  that  type  will  be  dis- 

317 


18  EARTHWORK 

cussed  first.     Power  shovels  may  also  be  classified  as  to  their  con- 
struction and  method  of  operation  as  follows : 

(1)  Those  having  the  machinery  mounted  on  a  fixed  platform, 
and  the  sphere  of  operation  limited  to  an  arc  of  about  200  degrees 
about  the  head  of  the  machine. 

(2)  Those  having  the  machinery  mounted  on  a  revolving  plat- 
form, and  the  sphere  of  operation  a  complete  circle,  the  center  of 
which  is  the  middle  of  the  machine. 

The  first  class  may  be  divided  into  three  types,  according  to  the 
manner  of  supporting  the  platform:  (a)  machines  mounted  on 
trucks  of  standard  gage,  used  largely  in  railroad  construction;  (b) 
machines  mounted  on  trucks  with  wheels  centered  at  other  than 
standard  gage,  and  used  in  various  classes  of  excavation ;  (c)  machines 
mounted  on  trucks  with  small,  broad-tired  wheels,  and  used  in  rail- 
road, street,  basement,  and  other  classes  of  construction. 

The  machines  of  type  (a)  are  generally  used  for  railroad  con- 
struction. A  wooden  or  steel  car  body  is  supported  on  two  4-wheel 
trucks  of  standard  make  and  gage.  The  crane,  which  is  generally  a 
structural-steel  frame,  is  so  arranged  that  it  can  be  lowered  to  pass 
under  overhead  bridges  and  through  tunnels. 

The  shovels  of  type  (b)  were  first  built,  and  are  still  used  on 
general  construction  work.  They  are  mounted  on  a  wide  wooden  or 
steel  framework,  or  car  body,  which  is  supported  on  4  small  wheels 
of  7-foot  or  8-foot  gage.  Great  stabiUty  is  thus  given  to  the  machine 
by  placing  it  near  the  ground  with  a  wide  base.  This  type  of  shovel 
can  be  readily  dismantled  and  transported  in  sections  on  cars, 
wagons,  or  boats,  and  is  very  serviceable  for  all  classes  of  earthwork 
on  account  of  its  portabiHty  and  adaptability. 

The  three  types  differ  principally  in  their  method  of  support, 
but  otherwise  are  similar  in  their  details  of  construction  and 
operation. 

FIXED=PLATFORM  TYPES 

Arrangement.  The  general  arrangement  is  similar  in  all  makes 
of  steam  shovel.  On  the  platform  or  car  body  is  located  the  operat- 
ing machinery  and  power  equipment;  the  boiler  at  the  rear  end,  the 
engines  near  the  center,  and  the  A-frame  and  crane  at  the  front  end, 
Fig.  14. 

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Car  Body.  The  car  body  consists  of  a  rigid,  structural-steel 
frame,  which  is  often  reinforced  with  durable  wooden  members  to 
assist  the  steel  shapes  in  resisting  the  severe  twisting  and  wrenching 
strains  during  operation.  On  the  platform  is  placed  a  wooden  or 
light  steel  frame,  which  is  covered  with  a  sheathing  of  wood  or  cor- 
rugated steel  to  form  an  enclosed  car.  Fig.  14.  Near  the  front  and 
on  each  side  of  the  platform  are  placed  jack  braces.  These  are 
heavy  cast-steel  brackets,  hinged  to  the  platform  and  carrying  screw 
jacks  at  their  outer  ends.  During  the  operation  of  the  shovel,  these 
braces  are  placed  at  right  angles  to  the  car  and  prevent  the  tipping 
of  the  front  end  during  the  swinging  of  the  crane  from  side  to  side. 

Power  Equipment.  The  power  equipment  generally  consists  of 
a  boiler  of  the  horizontal,  locomotive  type  for  the  larger  sizes,  or  a 
vertical,  submerged-flue  boiler  for  the  smaller  sizes  of  shovels,  and 
reversible  hoisting,  swinging,  and  thrusting  engines.  The  boiler  is 
fed  by  a  feed  pump  through  an  injector,  and  a  working  pressure  of 
125  pounds  is  used.  The  older  makes  of  shovel  used  1  engine  with 
3  drums  on  1  shaft  for  the  complete  operation;  but  the  newer 
types  are  equipped  with  separate,  horizontal,  reversible,  double- 
cylinder  engines  for  each  operation  of  hoisting,  swinging,  and  thrust- 
ing. Chains  or  wire  cables  are  wound  around  the  drums  and  attached 
to  the  dipper  handle  and  swinging  circle  and  thus  transmit  the  power 
for  the  operation  of  the  shovel. 

In  one  well-known  type  of  shovel  the  engines  are  mounted 
directly  on  the  swinging  circle  and  revolve  with  the  crane.  This 
arrangement  allows  more  room  on  the  platform  for  the  boiler,  and 
affords  direct  transmission  of  power  in  hoisting.  A  diagrammatic 
view  of  this  type  of  shovel  is  shown  in  Fig.  15. 

Table  I  gives  the  dimensions,  weights,  and  different  capacities 
of  a  standard  make  of  steam  shovel. 

The  cost  of  a  steam  shovel  varies  from  $120  to  $165  per  ton, 
the  larger  the  shovel,  the  less  the  cost  per  ton;  and  the  more  the 
total  weight,  the  greater  the  weight  per  cubic  yard  of  bucket. 

Excavating  Equipment.  The  excavating  equipment  is  located 
at  the  front  end  of  the  car  and  consists  of  the  boom  or  crane,  dipper 
handle,  and  dipper.  The  crane  is  made  in  two  sections  between 
which  the  dipper  handle  passes,  and  is  generally  in  the  form  of  a 
structural-steel  frame.    The  lower  end  of  the  boom  rests  on  the 


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swinging  circle  which  is  pivoted  to  the  front  end  of  the  platform. 
The  boom  revolves  with  the  swinging  circle.  The  upper  and  outer 
end  of  the  crane  is  connected  to  the  top  of  the  A-frame  mth  rods, 
and  has  a  sheave  over  which  the  hoisting  cable  passes  on  its  course 
from  hoisting  drum  to  dipper  handle.  The  latter  carries  the 
dipper  at  its  lower  end  and  moves  through  the  crane  and  over  a 
pinion  which  engages  a  toothed  rack  on  its  under  side.  The  dipper 
handle  is  usually  a  single  timber  of  hardwood,  reinforced  mth  steel 
plates  or  angles.  The  dipper  is  made  in  the  form  of  a  scoop  with 
closed  sides,  open  top,  and  a  hinged  and  latched  door  at  the  bottom. 
It  is  made  of  heavy  steel  plates  reinforced  at  top  and  bottom  with 
steel  bars.  The  top  or  front  edge  is  provided  with  a  sharp,  heavy- 
steel  cutting  edge,  or  manganese-steel  teeth.  The  bottom  of  the 
bucket  is  of  heavy  steel,  hinged  to  the  rear  side  and  closed  by  a 
spring  latch  on  the  front  side.  The  operation  of  the  bottom  door 
is  controlled  by  a  small  line  which  leads  from  the  door  to  the  side  of 
the  boom,  where  the  cranesman  stands.  Other  types  of  buckets  or 
dippers  may  be  used  wdth  the  steam  shovel,  for  various  classes  of 
excavation,  but,  as  they  are  largely  used  for  dredging,  their  con- 
struction and  use  will  be  described  under  the  section  on  "Floating 
Excavators". 

Method  of  Operation.  A  steam  shovel  of  the  first  class  is  gen- 
erally operated  by  a  crew  of  7  men;  an  engineer,  a  cranesman,  a 
fireman,  and  4  laborers.  The  engineer  and  cranesman  directly  con- 
trol the  movements  of  the  machine.  The  fireman  keeps  the  boiler 
supplied  with  fuel  and  water  and  sees  that  the  machinery  is  in  good 
running  order.  The  laborers  are  generally  under  the  direct  control 
of  the  cranesman  and  their  duties  consist  in  the  breaking  down  of 
high  banks,  assisting  in  the  loading  of  the  dipper,  leveling  the  surface 
in  front  of  the  machine,  laying  the  new  track,  operating  the  jack 
braces,  and  for  general  service  about  the  shovel.  In  rock  excava- 
tion, from  2  to  6  extra  laborers  are  required  for  breaking  up  the 
rock,  mud-capping,  etc. 

The  engineer  stands  at  the  set  of  levers  and  brakes  which  are 
located  in  front  of  the  machinery.  The  cranesman  stands  on  a  small 
platform  on  the  right  side  and  near  the  lower  end  of  the  crane.  The 
former  controls  and  directs  the  raising  and  lowering  of  the  dipper, 
the  swinging  of  the  crane,  and  the  traction  of  the  whole  machine. 

323 


24  EARTHWORK 

The  cranesman  controls  the  operation  of  the  dipper,  and  of  the 
dipper  handle,  regulating  the  depth  of  cut,  releasing  the  dipper 
from  the  bank  and  emptying  it  into  the  car,  wagon,  or  spoil  bank. 

The  process  of  excavation  commences  with  the  dipper  handle 
nearly  vertical  and  the  dipper  resting  on  the  floor  of  the  pit  with  the 
cutting  edge  directed  toward  the  bank.  The  engineer  then  moves 
a  lever  throwing  the  hoisting  drum  into  gear  and  starting  the  engine. 
The  revolution  of  the  hoisting  drum  winds  up  the  hoisting  hne  and 
pulls  the  dipper  upward.  Simultaneously,  the  cranesman  starts  the 
thrusting  engine  and  moves  the  dipper  handle  forward  as  the  dipper 
rises.  These  two  motions  must  be  made  smoothly  and  coordinately 
or  the  hoisting  engine  will  be  stalled  and  the  whole  machine  tipped 
suddenly  forward.  When  the  shovel  has  reached  the  top  of  the  cut 
or  its  highest  practicable  position,  the  engineer  throws  the  hoisting 
drum  out  of  gear  and  sets  the  friction  clutch  with  a  foot  brake,  thus 
bringing  the  dipper  to  a  stop.  Immediately,  the  cranesman  releases 
his  brake  and  slightly  reverses  the  thrusting  engine  which  thus 
draws  back  the  dipper  handle  and  withdraws  the  dipper  from  the 
face  of  the  excavation. 

When  the  dipper  digs  clear  of  the  excavation  it  is  unnecessary 
to  release  it  as  described  for  the  last  motion.  The  engineer  then 
starts  the  swinging  engine  into  operation  and  moves  the  crane  to 
the  side  until  the  dipper  is  over  the  dumping  place.  With  a  foot 
brake  he  sets  the  friction  clutch  controlling  the  swinging  drums 
and  stops  the  side  wise  motion  of  the  crane.  The  cranesman  then 
pulls  the  latch  rope,  which  opens  the  latch  and  allows  the  door  at 
the  bottom  of  the  dipper  to  drop  and  to  release  the  contents.  The 
engineer  then  releases  the  friction  clutch  by  the  foot  brakes  and 
reverses  the  swinging  engine,  pulling  the  crane  and  dipper  back  to 
position  for  the  next  cut.  As  the  boom  is  swung  around,  the 
engineer  gradually  releases  the  friction  clutch  of  the  hoisting  drum 
and  allows  the  dipper  to  slowly  drop  toward  the  bottom  of  the  cut. 
When  near  the  point  of  commencing  the  new  cut  and  as  the  dipper 
handle  approaches  a  vertical  position,  the  cranesman  releases  the 
friction  clutch  on  the  hoisting  engine  with  his  foot  brake.  Thus, 
as  the  last  part  of  the  drop  is  made  by  the  dipper,  it  is  also  brought 
into  proper  position  and  the  length  of  the  dipper  arm  regulated  for 
the  commencement  of  the  new  cut.    As  the  dipper  drops  into  place* 

324 


EARTHWORK 


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the  bottom  door  closes  and  latches  by  its  own  weight.  The  time 
required  to  make  a  complete  swing  depends  upon  the  character  of 
the  material  and  the  skill  of  the  operator,  but  under  ordinary  con- 
ditions this  should  average  between  20  and  40  seconds. 

After  the  entire  face  of  the  cut  has  been  removed  within  reach 
of  the  dipper,  the  shovel  is  moved  ahead.  When  the  shovel  moves 
on  a  track,  a  new  section  of  track  is  laid  ahead  of  the  section  on  which 
the  machine  rests.  The  laborers  release  the  jack  screws  of  the 
braces,  and  the  engineer  throws  the  propelling  gear  into  place,  starts 
the  engine,  and  the  shovel  moves  ahead  3  to  5  feet.  The  jack  braces 
are  then  set  into  position,  the  wheels  are  blocked,  and  the  shovel  is 


Fig.  16.     Diagram  of  Limitations  of  Atlantic  Steam  Shovels 


ready  for  another  cut.  The  maximum  width  of  cut  depends  upon 
the  size  of  shovel,  length  of  crane,  height  of  face,  etc.,  and  varies 
from  15  feet  to  30  feet.  The  shovel  may  cut  on  a  level  or  slightly 
descending  grade  and  by  working  back  and  forth  on  different  levels 
may  excavate  a  cut  of  almost  any  depth  and  width. 

The  steam  shovel  of  the  fixed-platform  class  will  excavate  any 
material  except  solid  rock,  which  must  first  be  blasted  down  and 
broken  up  into  pieces  small  enough  for  the  dipper  to  handle.  The 
excavated  material  may  be  dumped  into  and  carried  away  by:  (1) 
dump  wagons,  hauled  by  teams  or  by  traction  engines;  (2)  dump 
cars  holding  from  IJ  to  6  cubic  yards,  drawn  by  horses  or  dinkey 
locomotives  over  narrow-gage  track;  and  (3)  dump  cars  of  large 


326 


EARTHWORK  27 

size,  from  4  to  12  cubic  yards,  or  gondola  or  flat  cars,  hauled  by 
large-sized  locomotives  over  standard-gage  track. 

The  dimensions  and  working  limitations  of  a  well-known  make 
of  steam  shovel  of  this  class  are  shown  in  Fig.  16  and  Table  II. 

The  values  for  ''Digging  Radius  at  8-foot  Elevation",  given  in 
Table  II,  are  theoretical  figures  which  are  generally  not  realized  in 
practice.  It  would  be  conservative  to  use  values  of  from  60  per 
cent  to  80  per  cent  of  those  given  in  the  table  for  actual  working 
conditions. 

The  output  of  a  steam  shovel  depends  on  its  size,  the  character 
of  the  material  to  be  excavated,  the  efficiency  of  the  crew,  climatic 
conditions,  location  of  material  with  relation  to  the  shovel,  relation 
of  shovel  to  point  of  dumping,  efficiency  of  wagon  or  car  service, 
etc.  When  w^orking  under  favorable  conditions,  the  maximum 
working  capacity  of  a  shovel  will  average  about  one-half  of  its 
theoretical  capacity  as  rated  by  the  manufacturers.  A  shovel  is 
generally  in  actual  operation  about  40  per  cent  of  the  working  time. 
The  remainder  of  the  time  is  spent  in  waiting  for  cars  or  wagons, 
and  delays  for  repairs,  coaling,  watering,  oiling,  etc.  The  log  of 
efficient  shovel  operation  under  favorable  working  conditions  would 
be  about  as  follows: 


Time 

Operation 

(per  cent) 

►ving  shovel 

10 

;akiiig  up  rock,  mucking,  etc. 

10 

iting  for  cars  or  wagons 

15 

pairs 

5 

iual  loading 

60 

Total  100 

Table  III  gives  the  actual  output  of  about  fifty  shovels,  which 
were  in  actual  operation  for  several  wrecks.  These  records  were 
collected  by  Mr.  R.  T.  Dana,  of  the  Construction  Service  Company 
of  New  York. 

Cost  of  Operation.  The  cost  of  operation  of  a  steam  shovel 
depends  upon  the  class  of  work,  the  kind  of  material  to  be  excavated, 
the  size  and  efficiency  of  the  machine,  the  peculiar  conditions  affect- 
ing each  job,  the  facilities  for  removing  the  material,  etc. 

Illustrative  Example.  The  type  of  shovel  in  general  use  for 
heavy  excavation  is  a  70-  or  80-ton  machine  equipped  with  a  2i-yard 

327 


28 


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EARTHWORK  29 

dipper.  In  making  a  cut  for  a  railroad  or  large  canal,  or  in  opening 
up  a  gravel  pit,  mine,  or  quarry,  the  shovel  ordinarily  makes  a  through 
cut  and  then  returns  on  a  parallel  cut,  dumping  into  wagons  or  cars 
which  move  along  the  previous  grade  at  a  higher  level.    A  typical 

Train  of  Pump  Cars 


Tram  of  Pump  cars        


Fig.  17.     Diagram  of  Shovel  Operation 

arrangement  would  be  as  shown  in  Fig.  17.  Under  such  conditions 
the  cost  of  operation  of  a  2J-yard  steam  shovel  in  the  excavation 
of  clay  and  gravel,  for  a  10-hour  day,  would  be  as  follows: 

Cost  of  Excavating  Clay  and  Gravel 


Labor: 

1  engineer 

$5.00 

1  cranesman 

3.50 

1  fireman 

2.50 

\  watchman,  @  $50  per  month 

1.00 

4  pitmen,  @  $1 .  75  each 

7.00 

1  team  and  driver  (hauling  coal, 

water,  etc.) 

3.50 

Total  labor,  per  day 

$22.50 

Fuel  and  Supplies: 

2h  tons  of  coal,  @,  $4.00 

$10.00 

Oil,  and  waste 

1.50 

Water 

.50 

Total  fuel  cost,  etc. 

$12.00 

General  and  Overhead  Expenses: 

Repairs 

$5.00 

Incidental  expenses 

2.00 

Depreciation  (5%  of  $12,000)* 

3.00 

Interest  (6%  of  $12,000)* 

3.60 

Total  general  cost 

$13.60 

Total  Cost  of  Operation  per  10-hour  Day  $48. 10 

Average  Daily  Excavation  (cu.  yd.)  1600 

Unit  Cost  of  Excavating  clay  and  gravel  per  cu.  yd.,  $48.10  -r- 1600  =      00 .  03 

The  same  steam  shovel  used  in  the  excavation  of  a  stiff  clay  or 

shale  would  probably  require  the  services  of  2  extra  laborers  at 

♦Based  on  a  20-year  life  and  200  working  days  per  year. 

329 


30 


EARTHWORK 


$1.75  per  day  each.  The  average  daily  excavation  would  be  1000 
cubic  yards,  and  the  cost  of  operation  would  be  about  $0.05  per 
cubic  yard. 

For  the  excavation  of  rock  which  requires  blasting,  the  addi- 
tional labor  and  expense  would  be  as  follows: 


Labor: 


Additional  Cost  of  Excavating  Rock 


4  pitmen, 
2  laborers, 


$1 .  75  each 
^  $1 .  50  each 


$7.00 
3.00 


$10.00 
$4.00 


Fuel: 

1  ton  of  coal,  @  $4.00 

Loosening  Materials: 

Dynamite,  caps,  fuse,  powder,  etc.  $1 .  50 

Total  Additional  Cost  of  Excavating  rock  $15 .  50 

Total  Cost  of  Operating  Shovel  in  SoHd  Rock  per  10-hour  Day  $63 .  60 

Average  Daily  Excavation  (cu.  yd.)  900 

Unit  Cost  of  Operation,  per  cu.  yd.,  $63,604-900=  00.07 

The  above  statement  does  not  include  the  cost  of  transporting 
the  shovel  to  and  from  the  job,  the  cost  of  living  and  camp  expenses, 
or  office  and  other  fixed  charges. 


Fig.  18.     Bucyrus  Shovel  Filling  Dump  Cars  with  Clay 

The  cost  of  the  disposal  of  the  excavated  material  varies  from 
nothing  when  the  material  is  dumped  upon  the  sides  of  the  excava- 
tion (highway  or  canal  construction  on  a  side  hill)  to  15  or  20  cents 


330 


EARTHWORK 


31 


331 


32 


EARTHWORK 


per  cubic  yard  when  the  material  must  be  hauled  for  a  long  distance 
and  spread.  The  disposal  consists  of  two  operations:  the  hauling; 
and  the  dumping.  The  cost  of  hauling  depends  on  the  type  of 
conveyance  used,  number  of  cars  in  train,  length  of  haul,  etc.  The 
cost  varies  from  3  to  12  cents  per  cubic  yard.  The  cost  of  dumping 
varies  from  J  cent  per  cubic  yard  for  wagons  to  IJ  cents  per  cubic 
yard  for  cars.  Fig.  18  shows  a  shovel  loading  a  train  of  side-dump 
cars  with  clay.  Fig.  19  shows  a  large  size  steam  shovel  loading  a 
train  of  box  cars  mth  limestone  in  a  cement  quarry. 

REVOLVINQ=PLATFORM  TYPES 

Arrangement.    There  are  several  makes  of  revolving  shovel 
which  are  alike  in  general  arrangement  and  construction.    The 


Fig.  20.     Type  1  Thew  Shovel  Mounted  upon  Car  Wheeld 
Courtesy  of  The  Thew  Automatic  Shovel  Company,  Lorain,  Ohio 

essential  features  of  the  revolving  shovel  are  a  lower  or  trUck  plat- 
form and  an  upper  or  revolving  platform  on  which  are  located  the 
operating  and  excavating  equipments.  A  typical  make  of  revolving 
shovel  is  shown  in  Fig.  20. 

Platforms.  The  lower  or  truck  platform  is  composed  of  a 
rectangular  structural-steel  framework  which  is  strongly  braced  and 
riveted.  This  platform  rests  on  2  steel  axles,  the  front  one  pivoted 
and  the  rear  one  fixed  *in  position.    On  the  rear  axle  is  located  a 


332 


EARTHWORK 


33 


sprocket  wheel,  which  is  chain-connected  to  the  engine  and  thus 
provides  for  the  traction  of  the  machine  under  its  own  power.  The 
turning  of  the  front  axle  governs  the  direction  of  the  tractive  move- 
ment of  the  shovel.    The  wheels  may  be  either  wide-tired  wood  or 


Fig.  21.     Details  of  Thew  Hoistinjr  Engine — Horizontal  Double 
Reversing  Type 

steel,  or  flanged  railroad  wheels  when  the  shovel  is  to  operate  on  a 
track.  Upon  the  top  of  the  platform  is  located  a  large  casting  which 
comprises  a  circular  gear,  the  roller  track  and  the  central  journal 
or  gudgeon,  which  supports  the  upper  platform  and  works. 

The  upper  or  revolving  frame  carries  the  machinery  and  lower 
end  of  boom  and  corresponds  to  the  car  body  of  the  fixed-platform 
class  of  shovel.  This  platform  is  a  rigid  framework  of  structural- 
steel  members  which  are  strongly  braced  and  riveted.  A  heavy  cast- 
steel  socket  is  located  on  the  lower  side  of  the  platform  and  rests  on 
the  journal  of  the  lower  frame.  The  whole  operating  mechanism 
can  revolve  in  a  complete  circle  about  the  stationary  lower  frame. 

Power  Equipment.  The  power  equipment  of  a  revolving  steam 
shovel  consists  of  a  vertical  boiler  and  independent  engines  for 
hoisting,  swinging,  and  thrusting. 

The  boiler  is  of  the  vertical,  submerged  multi-tubular  type,  and 
made  to  operate  under  a  working  pressure  of  from  100  pounds  to 
125  pounds.    The  boiler  feed  consists  of  an  ejector  and  a  pump, 


333 


34  EARTHWORK 

which  can  supply  water  to  the  boiler  while  the  shovel  is  in  operation. 
The  boiler  is  located  on  the  rear  end  of  the  upper  platform. 

The  engines  are  all  double-cylinder,  horizontal,  and  reversible. 
The  swinging  and  hoisting  engines  are  located  in  front  of  the  boiler 
near  the  front  end  of  the  upper  platform.  The  thrusting  engine  is 
located  on  the  upper  side  of  th^  crane  or  boom.  The  hoisting  drum 
is  controlled  by  a  friction  band  which  is  operated  by  a  foot  lever. 
Fig.  21  shows  the  swinging  and  hoisting  engines  of  a  well-known 
make  of  revolving  shovel.  The  thrusting  engine  in  several  makes 
is  of  the  double,  horizontal,  reversible  type  which  is  used  on  shovels 
of  the  fixed-platform  class.  One  make,  the  Thew  Automatic  Shovel, 
uses  a  very  unique  and  efficient  method  of  thrusting  or  crowding 
the  dipper.  A  carriage  or  trolley  to  which  is  hinged  the  upper  end 
of  the  dipper  arm,  moves  horizontally  along  a  track.  As  the  carriage 
moves  forward,  the  center  of  rotation  of  the  dipper  is  changed  and 
produces  a  prying  action.  The  crowding  motion  is  always  in  a 
horizontal  direction.  The  movement  of  the  carriage  is.  controlled 
by  the  cranesman,  who  operates  the  throttle  lever  of  the  crowding 
engine.  The  throttle  is  also  connected  to  a  "trip",  which  auto- 
matically shuts  off  the  steam  when  the  carriage  reaches  either  end 
of  the  trackway.  Fig.  20. 

(jrasoline  power  can  be  used  to  great  economic  advantage  when 
coal  is  high  in  price  and  inaccessible.  The  prime  mover  is  then  a 
gasoline  engine  which  is  mounted  on  the  rear  of  the  platform  and 
belt-connected  to  the  operating  units. 

The  upper  platform  is  provided  with  a  housing  of  wood  or  cor- 
rugated steel  for  the  enclosure  and  protection  of  the  machinery. 

Excavating  Equipment.  The  crane  or  boom  is  a  structural 
frame  of  steel,  or  of  steel  and  w^ood.  The  lower  end  is  hinged  to  the 
turntable  and  the  upper  end  is  supported  by  guy  rods  which  extend 
to  the  rear  corners  of  the  upper  frame.  The  boom  is  made  in  two 
sections  and  so  arranged  that  the  dipper  handle  may  move  between 
them.  Upon  the  upper  side  of  the  boom  is  located  the  thrusting 
mechanism. 

The  dipper  handle  is  of  steel,  or  hardwood  reinforced  with  steel 
plates.  The  lower  end  of  the  handle  is  attached  to  the  dipper. 
Upon  the  under  side  of  the  handle  is  the  steel-toothed  rack  which 
engages  the  pinion  of  the  shipper  shaft,  which  is  the  gear-operating 

334 


EARTHWORK  35 

mechanism  of  the  thrusting  engine.  In  the  Thew  shovel,  the  dipper 
handle  is  made  of  steel  and  in  two  sections;  the  lower  member  tele- 
scopes into  the  upper  section,  and  the  two  may  be  clamped  in  any 
position. 

The  dipper  is  usually  constructed  of  steel  plates  and  forgings. 
The  cutting  edge  is  usually  made  of  manganese  steel  and  for  hard 
soils  is  provided  with  tool-steel  teeth  which  can  be  removed  and 
replaced  when  worn  out  or  broken. 

Method  of  Operation.  A  revolving  steam  shovel  is  generally 
operated  by  a  crew  of  3  to  5  men;  an  engineer,  a  fireman,  and  1  to 
3  laborers.  The  engineer  controls  the  operation  of  the  machine. 
The  fireman  feeds  the  boiler  with  fuel  and  water  and  keeps  the 
machinery  oiled  and  greased.  The  laborers  haul  coal,  assist  in  the 
loading  of  the  shovel  in  hard  material,  break  down  the  bank,  plank 
the  floor  of  the  excavation  for  the  support  of  the  shovel,  etc.  The 
engineer  stands  at  the  set  of  levers  and  brakes  which  are  located 
near  the  front  end  of  the  upper  platform.  The  method  of  operation 
of  this  type  of  shovel  is  similar  to  that  of  the  fixed-platform  class, 
and  the  student  is  referred  to  the  detailed  description  given  under 
that  section.  Note,  however,  that  in  the  case  of  the  revolving 
shovel,  there  is  no  cranesman,  and  the  engineer  directly  controls 
the  three  operating  motions  of  hoisting,  swinging,  and  thrusting. 

The  revolving  shovel  will  excavate  any  class  of  material,  except 
solid  rock,  which  must  first  be  blasted  down  and  broken  into  pieces 
of  a  size  which  can  be  handled  by  the  dipper.  The  excavated 
material  may  be  dumped  into  spoil  banks  along  the  side  of  the 
excavation,  or  into  wagons  hauled  by  horses  or  traction  engines,  or 
into  dump  cars  hauled  by  dinkey  locomotives  over  a  narrow-gage 
track. 

The  dimensions  and  working  limitations  of  an  efficient  make  of 
revolving  steam  shovel  of  the  revolving-platform  class  are  given  in 
Fig.  22.  In  column  1  of  the  table  the  class  numbers  correspond 
to  dipper  capacities  of  |,  |,  1|  or  If ,  J  or  1  (for  shale  excavation), 
and  If  o*ibic  yards,  respectively. 

The  actual  working  capacities  of  revolving  shovels  depend 
upon  the  nature  of  the  material,  depth  of  cut,  efficiency  of  hauling 
equipment,  efficiency  of  engineer,  size,  capacity,  and  efficiency  of 
shovel,  etc.     In  ordinary  clay,  under  average  working  conditions, 

335 


336 


EARTHWORK 


37 


with  a  cut  of  from  5  feet  to  10  feet,  the  output  for  a  10-hour  day 
should  average  from  about  500  cubic  yards,  for  a  f -cubic  yard 
machine,  to  1000  cubic  yards  for  a  If -cubic  yard  machine. 

OPERATING  COSTS  OF  POWER  SHOVELS 

Revolving  Shovels.  The  revolving  shovel  is  one  of  the  most 
satisfactory  and  efficient  machines  for  the  excavation  of  dry  soils 
when  the  required  output  does  not  exceed  about  1000  cubic  yards 
per  day.  For  light  earthwork,  where  the  excavation  is  widely  dis- 
tributed over  a  wide  area  or  within  narrow  boundaries  for  long 


Qrant  Sfreet 


Fig.  23. 


Excavation  Diagram  for  Reinforced-Concrete  Building  Showing  Location  and 
Path  of  Shovel 


distances,  this  type  of  shovel  is  much  more  economical  than  its 
larger  and  heavier  prototypes  of  the  fixed-platform  class.  This 
character  of  work  comprises  allotment  grading,  highway  and  street 
grading,  railroad  construction,  cellar  and  reservoir  excavation,  sewer 
trench  work,  reclamation  projects,  stripping  of  quarries,  operation 
of  gravel  pits,  brick  yards,  etc. 

The  size  of  revolving  shovel  in  general  use  is  the  |-yard  dipper 
machine  equipped  with  traction  wheels.  The  shovel  begins  at  the 
surface  and  works  its  way  down  on  an  easy  slope  to  the  final  grade. 


337 


38  EARTHWORK 

Then  the  path  of  the  shovel  may  be  varied  to  suit  the  requirements 
of  the  job,  but  usually  it  assumes  the  form  of  a  series  of  parallel  lines. 
At  the  completion  of  the  work  the  shovel  can  pull  itself  up  a  tem- 
porary incline  by  means  of  a  cable  attached  to  a  "deadman"  or 
anchorage  located  in  the  original  surface  above.  The  path  of  a 
revolving  shovel  in  excavating  a  cellar  for  a  large  reinforced-con- 
erete  building  is  shown  in  Fig.  23. 

Illustrative  Example.  The  following  example  is  a  typical  case 
of  the  use  of  a  revolving  shovel  in  quarry,  gravel  pit,  or  similar  work, 
where  the  magnitude  of  the  excavation  warrants  the  installation  of 
a  transportation  equipment  of  track  and  trains  of  dump  cars.  The 
shovel  is  a  |-cubic  yard  dipper  machine  mounted  on  broad-tired 
wheels  which  move  over  heavy  planking.  The  material  is  a  glacial 
clay  fairly  free  from  rock  and  boulders  and  varying  in  depth  from 
nothing  to  6  feet.  The  material  is  dumped  into  6-cubic  yard  side- 
dump  cars  which  are  hauled  by  a  dinkey  engine  in  trains  of  4  cars 
each.  The  following  cost  schedule  is  based  on  a  10-hour  working 
day. 

Cost  of  Operating  a  Revolving  Shovel 
Labor: 


1  engineer 
1  fireman 
1  laborer 

$4.00 
2.50 
2.00 

Total  labor  cost,  per  day 

Fuel  and  Supplies: 

1  ton  coal,  @  $4.00 
I  gal.  cylinder  oil,.  @  40c 
-^  gallon  engine  oil,  @  36c 
Waste,  packing,  etc. 

$2.00 
.07 
.04 
.19 

$8.50 

Total  cost  of  fuel  and  supplies 

General  and  Overhead  Charges: 

Depreciation  (based  on  20-year  life) 
Interest,  @  6% 
Repairs,  and  incidentals 

$0.70 

.84 

1.00 

$2.30 

Total  fixed  charges 

$2.54 

Total  Cost  for  10-hour  Day 

$13.34 

Average  Daily  Output  (cu.  yd.)  300 

Unit  Cost  of  Revolving  Shovel  Operation,  per  cu.  yd., 

$13,344-300=  00.045 

338 


EARTHWORK  39 

In  cellar  and  reservoir  excavation,  where  the  average  cut  would 
be  10  feet  and  the  material  loam,  clay,  and  sand,  the  daily  output 
might  be  increased  to  a  daily  average  of  500  cubic  yards  by  the  use 
of  sufficient  cars  or  dump  wagons  to  keep  the  shovel  busy  during 
60  to  70  per  cent  of  its  working  time.  This  would  make  the  average 
operating  cost  about  3  cents  per  cubic  yard. 

In  street  gradings,  where  the  material  is  dense  and  compacted 
by  traffic  and  the  cut  shallow  or  an  average  of  1  foot,  the  conditions 
of  successful  operation  would  be  more  difficult  than  usual.  If  the 
shovel  were  properly  supplied  with  l|-cubic  yard  dump  wagons, 
and  efficiently  operated,  the  average  output  for  a  10-hour  day 
should  be  250  cubic  yards.  This  output  would  incur  an  operating 
cost  of  about  8  cents  per  cubic  yard. 

Electrically  Operated  Shovels.  Where  electric  power  is  avail- 
able in  large  quantities  and  at  a  low  cost,  recent  experience  has 
shown  the  economy  of  this  type  of  power  for  the  operation  of  power 
shovels. 

Advantages  of  Electric  Power.  Where  electric  power  is  inex- 
pensive, the  cost  of  operation  of  an  electric  ^^hovel  is  less  than  that 
of  a  steam  shovel;  with  electric  power  at  3  cents  per  kilowatt  hour, 
the  cost  of  operation  is  about  one-half  that  of  steam-power  machines. 
Under  favorable  supply  conditions,  the  use  of  electric  power  is  desir- 
able and  economical  for  the  following  reasons :  (1)  less  labor  required 
for  operation;  eliminates  the  fireman  and  the  shovel  becomes  a  one- 
man  machine;  (2)  eliminates  the  hauling  and  expense  of  coal  and 
water;  (3)  greater  economy  of  power;  as  power  is  used  only  when 
operating,  and  steam  must  be  kept  up  continuously  in  case  of  the 
steam  shovel;  (4)  operation  is  quieter,  steadier,  and  quicker  than  that 
of  the  steam  shovel;  (5)  eliminates  the  discomfort  of  freezing  pipes 
in  cold  weather  and  of  boiler  temperature  in  hot  weather;  and  (6) 
eliminates  the  trouble  of  banking  fires  at  night  and  the  delay  in 
getting  up  steam  at  the  commencement  of  work. 

Electrical  Equipment,  The  prime  mover  is  the  electric  motor 
which  may  be  operated  by  either  direct  or  alternating-current 
service.  The  wound-rotor  type  of  motor  is  used  for  direct-current 
service  and  the  compound-wound  motor  for  alternating-current 
service.  The  various  sizes  of  motors  for  the  various  capacities  of 
shovels  are  given  in  Table  IV. 

339 


40 


EARTHWORK 

TABLE  IV 
Sizes  of  Motors  for  Various  Shovel  Capacities 


Weight  of 

Shovel 

(tons) 

Size  of 
Dipper 
(cu.  yd.) 

Power  ob  Motors 

Hoist 
(h.  p.) 

Swing 
(h.  p.) 

Thrust 
(h.  p.) 

30 
35 
,      35 
35 
42 
65 
95 
100 

1 

u 
u 

11 

2 

3i 

4 

50 

50 

60 

75 

75 

100 

150 

200 

30 
30 
30 
35 
30 
35 
50 
80 

30 
30 
30 
35 
30 
35 
50 
80 

The  hoist  and  swing  motors  are  mounted  behind  their  respective 
engines  and  are  geared  to  them  through  reducing  gears.  The  thrust 
motor  is  mounted  on  the  upper  side  of  the  boom,  and  geared  to  the 
pinions  through  proper  reducing  gears. 

Shovel  service  is  particularly  severe  on  electric  equipment  on 
account  of  the  high  power  at  low  speed  and  the  quick  starting, 
stopping,  and  reversing  of  the  machinery.  The  sudden  stopping  of 
the  dipper  in  the  bank,  due  to  cutting  too  deep,  or  striking  an  obstruc- 
tion, or  the  sudden  stopping  of  the  boom  in  the  act  of  swinging  to 
one  side,  tends  to  stall  the  motor  and  burn  it  out.  The  use  of  auto- 
matic magnetic  controllers  and  magnet  switches  has  resulted  in  the 
efficient  control  and  protection  of  the  motor  against  such  overloads. 

On  revolving  shovels,  a  single-motor  drive  has  been  found  to 
be  the  more  satisfactory  on  account  of  the  economy  in  initial  cost 
and  the  simplicity  and  flexibility  of  operation. 

The  current  is  taken  from  trolley  wires,  or  a  transformer  on  a 
high-power  line,  and  is  received  through  the  truck  by  wire  cables. 
In  the  case  of  revolving  shovels  the  current  is  transmitted  to  the 
motor  above  through  copper  rings  on  the  truck  frame  and  carbon 
brushes  suspended  from  the  rotating  turntable. 

Field  of  Usefulness.  The  electric-power  shovel  is  especially 
adapted  for  underground  service  in  mines  and  tunnels,  for  plant 
service  in  the  handhng  of  ores,  coal,  fertilizers,  etc.,  for  excavation 
in  large  cities,  for  electric  street-railway  construction,  and  for  brick 
yards,  gravel  pits,  etc.  Probably  the  best  field  of  service  for  the 
electric-power  shovel  at  the  present  time  is  the  use  of  the  electri- 
cally operated  revolving  shovel  in  the  construction  of  city  and  inter- 


340 


EARTHWORK 


41 


urban  electric  lines.  The  track  trenching  usually  requires  the 
shallow  excavation  of  dense,  hard  material  to  a  uniform  grade,  and 
the  revolving  shovel  is  the  most  efficient  excavator  for  this  class  of 
work.  An  electrically  operated  revolving  shovel  is  shown  in  Fig.  24. 
Efficiency  and  Economy  of  Power  Shovels.  The  steam  shovel 
is  one  of  the  most  universally  serviceable  and  efficient  of  modern 
excavators.     When  the  soil  is  sufficiently  dry  and  firm  to  support 


Fig.  24.     Electrically  Operated  Power  Shovel 
Courtesy  of  Westinghouse  Electric  and  Manufacturing  Company,  Pittsburgh,  Pennsylvania 


its  weight  and  the  work  is  of  sufficient  magnitude  to  warrant  its 
use,  it  can  be  used  economically  for  all  classes  of  earthwork.  Hand 
shoveling  has  been  almost  entirely  superseded  by  power-machine 
shoveling  on  work  where  the  amount  of  w^ork  will  justify  the  cost 
of  installation  of  the  plant.  The  relative  economy  of  the  two 
methods  may  be  determined  approximately  by  estimating  the  cost 
per  cubic  yard  by  hand  labor  and  the  same  cost  by  power  machine. 


341 


42  -  EARTHWORK 

including  in  the  total  cost  by  the  latter  method  the  items  of  plant 
installation,  depreciation,  interest,  and  repairs. 

A  comparison  can  be  made  for  the  excavation  of  ordinary  soil 
of  loam,  clay,  and  sand,  under  average  working  conditions,  between 
power-shovel  and  hand  labor.  This  discussion  cannot  be  exact  as 
there  are  many  indeterminate  and  variable  conditions  of  soil,  labor 
efficiency,  etc.,  which  will  affect  the  results  for  the  peculiar  condi- 
tions of  each  case.  However,  the  student  is  urged  to  study  the 
method  of  analysis,  as  it  can  easily  be  applied  to  the  investigation 
of  other  methods  and  of  other  types  of  machinery. 

Illustrative  Example.  Let  us  assume  a  loam  and  clay  soil  with 
few  boulders  or  obstructions;  the  hauling  to  be  done  by  2-yard  dump 
wagons  of  sufficient  number  to  keep  the  hand  shovelers  or  power 
shovel  busy;  the  cut  to  average  8  feet,  and  runways  to  be  arranged 
for  the  incoming  and  outgoing  teams;  the  material  first  to  be  loosened 
in  the  case  of  hand  shoveling. 

Cost  of  Shoveling  by  Hand 

Loosening: 

1  plow  team,  with  driver  and  plow  holder; 
Team,  plow,  and  driver  $3 .  50 

Plow  holder  1.50 


Total  labor  cost,  per  day  $5 .  00 

Repairs,  depreciation,  etc.  1 .  00 

Total  Cost  of  Loosening  $6 .  00 

Total  Amount  of  Loosened  Material  (cu.  yd.)  400 

Unit  Cost  of  Loosening  Material,  per  cu.  yd.,  $6.00-v-400=        00.015 

Shoveling  and  Loading: 

One  man  can  shovel  and  load  about  20  cubic  yards  per  10-hour  day. 
Hence  the  plow  should  loosen  enough  material  to  keep  20  men  busy.  Load- 
ing dump  wagons,  these  men  can  work  efficiently  in  4  groups  of  5  men  each. 
Each  group  of  5  men  can  load  on  an  average  6  wagons  per  hour  or  50  wagons 
per  10-hour  day,  allowing  for  delays. 

1  foreman  $  3.00 

20  laborers,  @  $1 .50  each  30 .  00 

Total  labor  cost,  per  day  $33 .  00 

Repairs,  incidentals,  etc.  1 .  00 

Total  Cost  of  Shoveling  and  Loading  $34.00 
Total  Amount  of  Earth  Handled  (cu.  yd.)                        400 

Unit  Cost  of  ShoveUng  and  Loading,  per  cu.  yd.,  $34.00-^400  =  00 .  085 

Total  Cost  of  Hand  ShoveUng  400  cubic  yards  40 .  00 

Unit  Cost  of  Hand  Shoveling,  per  cu.  yd.,  $40.00^400  =  00 .  10 

342 


EARTHWORK  43 

Assume  also  a  revolving  steam  shovel  equipped  with  a  |-yard 
dipper  and  operated  by  an  engineer,  fireman,  and  2  pitmen.  With 
good  wagon  service,  the  average  output  will  be  500  cubic  yards  per 
10-hour  day.    The  shovel  will  load  on  an  average  30  wagons  per  hour. 

Cost  of  Power  Shoveling 

Labor: 


1  engineer 

$5.00 

1  fireman 

2.50 

2  pitmen,  @  $1.50  each 

3.00 

Total  labor  cost,  per  day 

$10.50 

Fuel  and  Supplies: 

f  ton  coal,  @  $4.00 

$3.00 

Oil  and  supplies 

1.00 

Total  fuel  and  supplies 

$4.00 

General  and  Overhead  Charges: 

Depreciation* 

$1.00 

Interest  t 

1.20 

Repairs  and  Incidentals 

1.80 

Total  fixed  charge 

$4.00 

Total  Cost  of  Operation  per  10-hour  Day  $18 .  50 

Average  Daily  Output  (cu.  yd.)  500 

Unit  Cost  of  Power  Shovel  Operation,  per  cu.  yd., 

$18,504-500=  00.037 

The  above  data  show  that  the  output  is  increased  by  25  per 
cent  at  a  reduction  in  cost  of  65  per  cent  by  the  use  of  the  steam 
shovel.  The  average  loading  time  by  hand  shoveling  was  assumed 
as  10  minutes  and  for  the  steam  shovel  as  2  minutes.  This  means 
a  saving  of  about  4  minutes  per  cubic  yard  by  the  use  of  the  steam 
shovel. 

If  the  teams  are  paid  at  the  rate  of  50  cents  per  hour  for  a 
10-hour  day,  the  economy  in  the  value  of  the  team  time  saved, 
for  different  shovel  outputs,  will  be  as  follows: 

Economy  in  Team  Cost 

300  cu.  yd.  per  10-hr.  day,  at  3t  min.  900  min.  or  15  hrs.  @  50c $7.50 

400  cu.  yd.  per  10-hr.  day,  at  3t  min.  1200  min.  or  20  hrs.  @  50c  10.00 

500  cu.  yd.  per  10-hr.  day,  at  3^  min.  1500  min.  or  25  hrs.  @  50c  12 .  50 

600  cu.  yd.  per  10-hr.  day,  at  3$  min.  1800  min.  or  30  hrs.  @  50c  15.00 

*  Based  on  5  per  cent  and  20-year  life. 
t  Based  on  6  per  cent  and  20-year  life. 
t  Value  of  3  minutes  is  used  as  being  conservative. 

343 


44  EARTHWORK 

Thus  it  will  be  noted  that  the  saving  in  team  time  per  10-hour 
day,  on  the  basis  of  an  efficient  shovel  operation  of  600  cubic  yards, 
is  nearly  enough  to  pay  for  the  operating  cost  of  the  shovel.  Hence 
it  is  likewise  true  that  the  economy  resulting  from  the  efficient  use 
of  a  power  shovel  is  often  equal  to  the  entire  cost  of  shoveling  and 
loading  by  hand  methods.  If  the  job  comprised  the  removal  of 
45,000  cubic  yards  and  hand  shoveling  cost  10  cents  per  cubic  yard, 
the  use  of  a  steam  revolving  shovel  would  effect  a  saving  sufficient 
to  pay  for  the  cost  of  the  machine. 

DREDGES 

DRY=LAND  EXCAVATORS 

Preliminary  Discussion.  The  steam  shovel  is  not  well  adapted 
to  earthwork  operations  on  wet  or  soft  soils  on  account  of  the  con- 
centration of  the  heavy  load  of  the  machine  and  loaded  dipper  over 
a  long,  narrow  area.  The  crane  or  boom  of  the  power  shovel  is 
short,  of  heavy  construction,  and  produces  great  pressure  over  a 
small  area  of  base.  Hence,  for  the  excavation  of  soft  and  wet  soils, 
especially  on  reclamation  projects,  it  became  necessary  to  devise  a 
machine,  similar  in  construction  and  operation  to  the  power  shovel, 
but  with  the  load  distributed  over  a  wide  base  and  with  a  long  boom 
for  the  direct  removal  of  the  excavated  material  to  spoil  banks 
adjacent  to  the  excavation.    Thus  was  developed  the  dredge. 

Classification.  Dredges  may  be  divided  into  two  different 
classes:  dry-land  excavators,  and  floating  excavators.  The  different 
types  of  dry-land  excavators  will  be  considered  in  this  section  and 
the  different  types  of  floating  excavators  in  the  following  section. 

Dry-land  excavators  are  those  which  move  over  and  operate 
from  the  surface  of  the  land.  They  may  be  classified  as  to  their 
construction  and  method  of  operation  as  follows :  scraper  excavators, 
templet  excavators,  wheel  excavators,  tower  excavators,  and  walk- 
ing excavators.  Scraper  excavators  may  be  subdivided  into 
two  general  classes,  as  to  their  method  of  operation :  the  stationary 
dredge  with  pivoted  boom,  and  the  revolving  dredge  or  excavator. 

STATIONARY  SCRAPER  EXCAVATOR 

During  the  past  decade,  the  reclamation  of  thousands  of  acres 
of  wet  land  in  the  Middle  West  and  South,  has  required  the  con- 

344 


EARTHWORK 


45 


struction  of  drainage  ditches.  For  this  work  the  stationary  dredge, 
a  light  portable  type  of  excavator,  has  been  designed  particularly 
for  the  economical  excavation  of  the  smaller  sized  channels.  This 
machine  is  stationary  only  as  regards  its  position  during  excavation, 
as  it  is  a  traction  machine. 

Construction.  The  machine  consists  of  a  framework  of  stand- 
ard structural-steel  shapes,  supported  on  two  trucks.  Each  truck 
comprises  a  heavy  steel  axle  with  two  broad-tired  steel  wheels  of 
5-foot  to  6-foot  diameter.  Some  makes  of  excavator  are  supported 
on  cateroillar  tractors  so  as  to  distribute  the  load  more  uniformly 


Fig.  25.     Caterpillar  Tractor 

over  a  larger  area  of  wet  soil.  As  in  the  view  of  one  of  these  tractors 
in  Fig.  25,  the  framework  supports  the  operating  and  excavating 
equipment.     An  excavator  loading  cars  is  shown  in  Fig.  26. 

Operating  Equipment.  Near  the  front  end  of  the  platform  are 
placed  the  operating  drums  and  gears  which  are  belt-connected  to  a 
kerosene  or  gasoline  engine  mounted  near  the  rear  end  of  the  plat- 
form. The  hoisting  and  drag-line  drums  are  controlled  by  friction 
clutches  operated  by  levers. 

These  light  excavators  are  operated  almost  entirely  by  internal- 
combustion  engines  as  they  are  clean,  compact,  easy  to  operate,  and 
economical.    A  25-  to  50-horsepowei:  kerosene  or  gasoline  engine  is 


345 


46 


EARTHWORK 


s  ^ 
1^ 


;!! 


346 


EARTHWORK  47 

used,  depending  on  size  and  capacity  of  machine.  With  a  |-yard 
bucket  and  50-foot  boom,  a  40-horsepower  engine  is  of  sufficient  size 
to  furnish  the  power  for  the  excavation  of  all  classes  of  soils.  The 
engine  is  equipped  with  forced-oil  feeder,  gear-driven  magneto,  car- 
bureter, throttle,  governor,  large  oil  tank,  etc. 

Excavating  Equipment.  The  excavating  equipment  consists  of 
the  boom,  and  bucket  or  scoop.  The  boom  is  made  of  steel  channels 
latticed  and  braced  with  truss  rods.  The  lower  end  rests  in  a  uni- 
versal joint  at  the  front  end  of  the  platform,  and  the  upper  end  is 
supported  from  the  A-frame  by  cables  and  carries  the  sheave  over 
which  the  hoisting  cable  passes.  The  bucket  is  a  steel  scoop  pro- 
vided with  tool-steel  teeth  for  the  excavation  of  dense  and  hard  soils. 

Method  of  Operation.  One  man  is  required  to  operate  the 
machine  and  he  stands  at  the  front  and  controls  the  machine  by  a 
set  of  levers.  The  bucket  is  lowered  to  the  surface  by  releasing  the 
hoisting  line.  Then  the  drag  line  is  hauled  in  and  this  pulls  the 
bucket  toward  the  machine,  SQOoping  up  a  thin  slice  of  earth  during 
its  progress.  When  the  bucket  is  near  the  machine  and  filled,  the 
boom  is  swung  to  one  side  until  the  bucket  is  over  the  spoil  bank, 
when  it  is  inverted  and  dumped. 

Field  of  Usefulness.  The  stationary  dredge  of  the  light,  port- 
able type  of  construction  is  rapidly  developing  a  wide  field  of  eco- 
nomic service  in  earthwork.  Being  simple  and  light  in  construction, 
the  machine  can  be  set  up  in  a  short  time  and  can  move  readily  over 
fairly  level  ground. 

In  reclamation  work,  this  excavator  is  efficient  in  the  excava- 
tion of  open  ditches  up  to  about  40  feet  in  width.  It  can  be  used 
advantageously  for  the  cleaning  out  of  old  ditches  which  have 
become  silted  up.  For  the  excavation  and  back  filling  of  trenches 
for  drain  tile  from  24  inches  to  42  inches  in  diameter,  the  scraper 
excavator  is  very  efficient. 

When  highway  and  railroad  work  are  in  wet  soils,  the  light 
scraper  excavator  has"  proved  its  adaptability  in  the  construction  of 
cuts  and  embankments.  The  cuts  can  be  made  to  any  desired  side 
slope  and  to  any  depth  or  width  by  making  one  or  more  trips  on  the 
same  or  different  levels.  The  machine  can  borrow  the  material 
from  one  or  both  sides  and  construct  the  side  ditches  in  the  making 
of  embankments. 


347 


48  EARTHWORK 

The  cost  of  operation  will  vary  from  4  cents  to  10  cents  per 
cubic  yard  for  an  output  of  from  1000  to  500  cubic  yards  per  10- 
hour  day,  depending  on  soil  conditions,  efficiency  of  the  operator, 
etc.  The  machine  is  generally  operated  by  one  man  and  one  or  more 
men  are  necessary  for  general  service  in  the  pit  and  about  the  work. 

REVOLVING  EXCAVATOR 

Methods  of  Mounting.  The  most  generally  used  type  of  dry- 
land scraper-bucket  excavator  is  the  revolving  type.  These  machines 
may  be  mounted  in  three  different  ways  as  follows: 

(1)  On  skids  and  rollers,  when  the  machine  travels  over  the 
planks  laid  on  the  surface.  The  machine  moves  ahead  by  pulling 
itself  up  to  its  bucket,  which  acts  as  an  anchor. 

(2)  On  trucks,  when  the  machine  is  mounted  on  small,  steel, 
4-wheel  trucks.  The  machine  moves  ahead  as  in  the  case  of 
skids  and  rollers. 

(3)  On  caterpillar  tractors,  when  the  machine  is  supported  on 
4  moving  platforms  which  are  especially  adapted  for  soft  soil  condi- 
tions and  allow  the  machine  to  move  ahead  without  the  use  of 
planking,  tracks,  etc. 

Construction.  The  essential  parts  of  a  scraper-bucket  excava- 
tor are  the  substructure,  consisting  of  the  upper  and  lower  platforms 
and  turntable;  the  power  equipment;  and  the  excavating  equipment. 
These  essential  parts  are  practically  the  same,  as  regards  their 
method  of  operation,  for  all  makes  of  drag-line  excavator.  These 
parts  are  shown  in  Fig.  27. 

The  substructure  consists  of  a  lower  platform,  an  intermediate 
turntable  and  an  upper  platform.  The  lower  frame  consists  of  a 
rectangular  framework  of  structural-steel  shapes.  The  frame  is 
mounted  in  one  of  three  ways  stated  above.  Upon  the  upper  sur- 
face of  the  lower  platform  is  fastened  the  track  upon  which  runs  the 
moving  circle.  In  the  center  is  located  the  lower  section  of  the 
central  pivot. 

The  turntable  consists  of  a  swinging  circle,  which  is  a  steel 
frame  carrying  a  series  of  flanged  wheels. 

The  upper  framework  or  platform  consists  of  steel  shapes 
framed  rigidly  together.  Upon  the  lower  surface  of  its  frame  is 
placed  the  upper  section  of  the  central  pivot. 

348 


*^    \ 


349 


50 


EARTHWORK 


Power  Equipment.  Scraper-bucket  or  drag-line  excavators  may 
be  operated  by  steam,  electric,  or  gasoline  power.  The  steam  equip- 
ment is  the  one  generally  used  and  will  be  discussed  first. 

Steam  Poiver.  The  power  equipment  of  a  steam-power  exca- 
vator consists  of  the  boiler,  steam  pump,  injector,  feed- water  heater, 
main,  and  swing  engines.  The  boiler  may  be  either  of  the  horizontal, 
locomotive  type  or  of  the  vertical,  submerged-tube  type.  The 
former  is  the  more  efficient  for  hard  usage  and  the  latter  the  more 
economical  of  space.  A  steam  pressure  of  about  125  pounds  is  ordi- 
narily maintained  under  average  conditions.     A  steam  pump  of  the 


Fig.  28.     Interior  View  of  Scraper  Bucket  Excavator.     A,  A-Frame;  B,  Boiler;  C, 

Hoisting  Engine;  D,  Feed-Water  Heater;  E,  Deck  Winch;  F,  Swinging 

Engine;  G,  Feed-Water  Pump 

Courtesy  of  Lidgerwood  Manufacturing  Company,  New  York  City 

standard  duplex  type  is  generally  connected  to  a  water  supply  from 
which  the  boiler  is  furnished  by  an  injector.  A  feed-water  heater 
is  often  necessary  to  purify  alkali  waters  before  they  are  admitted 
to  the  boiler. 

The  main  or  hoisting  engines  are  of  the  horizontal,  double- 
cylinder,  friction-drum  type.  The  swinging  engine  may  be  a  part 
of  the  main  engine  or  a  separate  mechanism.  The  latter  method  is 
the  more  satisfactory.  The  hoisting  engine  in  this  case  has  two 
drums,  one  for  the  hoisting  cable  and  the  other  for  the  drag  line. 
These  drums  are  often  controlled  by  double-band  outside  friction 


350 


EARTHWORK  51 

clutches  operated  by  auxiliary  steam  rams.  The  swinging  engine  is 
of  the  steam,  reverse  type  and  drives,  through  a  chain  of  gears,  a 
pinion  which  operates  the  large  circular  rack  on  the  lower  frame. 
The  power  equipment  of  a  typical  drag-line  excavator  is  shown  in 
Fig.  28. 

Electric  Power.  Where  electric  power  is  available  and  reason- 
able in  cost,  it  is  advisable  to  use  electric  motors,  in  place  of  the 
steam-boiler  equipment.  Either  alternating  or  direct  current  may 
be  used.  The  motors  may  be  gear  or  belt-connected  to  the  shafts 
of  the  hoisting  and  swinging  engines.  The  drums  of  these  engines 
are  controlled  by  outside-band  friction  clutches,  which  are  actuated 
by  pneumatic-thrust  cylinders.  A  small  belt-connected  air  com- 
pressor with  receiving  tank  supplies  the  compressed  air  for  the  rams. 
On  a  120-ton  machine  equipped  -mth  a  2|-yard  dipper,  a  115-horse- 
power,  60-cycle,  3-phase  motor  for  the  hoisting  engine,  and  a  50- 
horsepower,  60-cycle,  3-phase  motor  for  the  swinging  engine  are 
suitable  for  the  power  equipment.  The  cost  of  current  will  vary 
from  i  to  1  cent  per  cubic  yard,  depending  on  the  market  price. 

The  reliability,  cleanliness,  and  economy  of  this  form  of  power 
are  strong  factors  in  favor  of  its  use.  It  has  proved  very  advanta- 
geous in  reclamation  work  in  the  arid  regions  of  the  West,  where  coal 
and  water  are  scarce  and  expensive,  and  electric  power  is  available 
from  near-by  transmission  lines  of  water-power  plants. 

Gasoline  Power,  Gasoline  and  kerosene  engines  have  been 
successfully  used  in  the  operation  of  the  machinery  of  the  smaller 
sizes  of  scraper-bucket  excavators.  The  engine  is  mounted  on  a 
base  just  to  the  rear  of.  the  drum  mechanism  to  which  it  is  belt- 
connected.  A  50-  to  80-horsepower  engine  is  necessary  for  the 
efficient  operation  of  hoist  and  swinging  engines.  The  drums  of 
the  hoisting  mechanism  are  provided  with  outside-band  friction 
clutches,  which  are  controlled  by  pneumatic-thrust  cylinders. 
Double-cone  friction  clutches  are  used  to  operate  the  drums  of  the 
swinging  mechanism.  A  small  air  compressor  actuated  by  a  belt 
connection  with  the  engine  furnishes  compressed  air  to  a  receiving 
tank.  The  air  is  supplied  to  the  thrust  cylinders,  which  operate 
the  band  friction  clutches  on  the  drums.  A  water  tank  for  supplying 
water  to  cool  the  engine  cylinder  and  a  gasoline  supply  tank  are  also 
placed  on  the  upper  platform  near  the  engine. 

351 


52  EARTHWORK 

The  gasoline  engine  is  the  most  economical*" type  of  prime 
mover  or  power  producer  in  locaUties  where  coal  and  water  are 
scarce  and  expensive,  and  electric  power  is  not  available. 

Excavating  Equipment.  The  excavating  equipment  consists  of 
the  A-frame,  boom,  and  bucket. 

The  A-frame  is  generally  a  framework,  shaped  like  the  letter  A, 
composed  of  wooden  or  steel  members.  This  frame  is  located  near 
the  front  end  of  the  platform.  The  top  of  the  boom  is*  connected 
by  cable  with  the  top  of  the  frame  which  is  also  guyed  back  to  the 
two  rear  corners  of  the  platform.  The  top  of  the  boom  may  be 
raised  and  lowered  by  means  of  a  wire  cable,  which  passes  from  the 


Fig.  29.     Page  Scraper  Bucket 

end  of  the  boom  over  a  sheave  at  the  top  of  the  A-frame  and  thence 
down  to  the  deck  winch. 

The  boom  is  generally  a  steel  framework  which  is  pivoted  to 
the  front  end  of  the  platform.  The  upper  end  of  the  boom  is  framed 
so  as  to  form  a  boxing  for  one  or  more  sheaves  over  which  the  hoist- 
ing cable  passes. 

The  bucket  may  be  one  of  three  types:  the  scraper  bucket,  the 
clam-shell  bucket,  and  the  orange-peel  bucket.  The  last  two  types 
will  be  discussed  in  the  section  under  "Floating  Dipper  Dredges", 
Part  II.  The  scraper  bucket  is  the  type  generally  used  with  a 
drag-line  excavator.  It  consists  of  a  box-shaped  scoop  made  of 
heavily  reinforced,  shaped  steel  plates.  The  lower  front  edge  is 
the  cutting  edge  and  is  made  of  manganese  steel  and  for  hard  material 

352 


EARTHWORK  53 

is  provided  with  teeth.  There  are  several  makes  of  these  buckets, 
which  differ  only  in  their  details  of  construction.  The  Page  bucket 
is  shown  in  Fig.  29. 

Method  of  Operation.  A  steam-operated  machine  requires  the 
services  of  four  men :  an  engineer,  a  fireman,  and  two  laborers.  The 
engineer  stands  at  the  front  end  of  the  platform  and  by  means  of  the 
levers  and  brakes  controls  the  entire  operation.  The  fireman  keeps 
the  boiler  fed  with  fuel  and  water  and  has  general  supervision  of 
the  machinery.  The  laborers  act  as  pitmen  and  are  of  general  serv- 
ice about  the  machine.  The  fireman  can  be  eliminated  in  the  case 
of  the  excavators  operated  by  electric  motors  or  internal-combus- 
tion engines. 

The  operation  of  excavation  commences  with  the  bucket  in  the 
first  position  shown  in  Fig.  27.  The  engineer  releases  the  hoisting- 
line  and  drag-line  drums  and  allows  the  bucket  to  drop  to  the  surface, 
where  it  will  be  in  the  second  position  showTi  in  Fig.  27.  In  descend- 
ing, the  weight  of  the  bucket  maintains  its  vertical  position  and  forces 
the  cutting  edge  into  the  soil,  giving  it  an  initial  bite.  With  the  hoist- 
ing line  still  released,  the  operator  starts  up  the  drag-line  drum  and 
pulls  the  bucket  toward  the  machine.  The  first  pull  on  the  drag 
line  tilts  the  bucket  to  the  proper  position  for  the  penetration  of  the 
soil.  By  a  slight  manipulation  of  the  hoisting  line,  the  proper  angle 
of  the  bucket  may  be  kept  for  a  deep  cut  in  soft  soils  or  for  a  thin 
cut  in  hard  soils.  When  the  bucket  is  filled,  the  drag-line  drum  is 
set  and  the  hoisting  drum  is  started,  and  this  automatically  raises 
the  front  end  of  the  bucket  and  thereby  prevents  the  spilling  of  the 
contents  during  the  swing  to  the  spoil  bank.  The  front  end  of  the 
bucket  is  held  up  by  means  of  the  tension  of  the  dumping  line  which 
is  the  upper  branch  of  the  drag  line.  See  third  position  of  the 
bucket  in  Fig.  27.  When  the  dumping  position  is  reached,  the 
operator  releases  the  drag  line  and  the  bucket  revolves  into  a  vertical 
position  and  dumps.  The  tension  is  applied  or  released  by  pressure 
on  the  brake  lever  actuating  the  drag  line  and  hence  the  operation 
of  dumping  is  always  under  the  control  of  the  operator. 

Cost  of  Operation.  The  cost  of  operation  of  a  scraper-bucket 
excavator  depends  on  the  class  of  work,  the  kind  of  material  to  be 
handled,  the  size  of  the  machine,  the  efficiency  of  the  operator,  the 
character  and  cost  of  the  power  used,  etc. 

353 


54 


EARTHWOEK 


Illustrative  Example.  The  type  of  machine  in  general  use  is  a 
steam-power  excavator,  equipped  with  a  2|-yard  bucket.  Such  a 
machine,  on  ditch  or  railroad  construction  should  excavate  about 
1200  cubic  yards  of  loam  and  clay  during  a  10-hour  working  day. 
The  following  is  a  typical  case  of  the  cost  of  operation,  under  such 
conditions,  for  a  10-hour  day : 


Operating  Cost  of  Steam-Power  Scraper-Bucket  Excavator 


Labor: 


1  engineer  $5.00 

1  fireman  3.00 

2  laborers,  @  $1 .75  each  3 .  50 
1  team  and  driver  (hauling  coal,  etc.)  3.50 


Total  labor  cost,  per  day 

Fuel  and  Supplies: 

2  tons  of  coal,  @  $4.00 

$8.00 

Oil,  and  waste 

1.75 

Water 

0.35 

Total  fuel  and  supplies 

General  and  Overhead  Expenses: 

Repairs 

$4.00 

Incidental  expenses 

2.00 

Depreciation  (10%  of  $10,000)* 

5.00 

Interest  (6%  of  $10,000)* 

3.00 

Total  general  and  overhead  expense 


$15.00 


$10.10 


$14.00 


$39.10 


Total  Cost  of  Operation  for  10-hr.  Day 

Average  Daily  Excavation  (cu.  yd.)  1200 

Unit  Cost  of  Scraper-Bucket  Excavating,  cu.  yd.,  $39.10-M200  =  00.033 


Fig.  30.     Diagram  of  Limitations  of  Drag- Line  Excavators 
on  a  life  of  10  years  and  200  working  days  per  year. 


354 


EARTHWORK 


55 


Field  of  Usefulness.  The  field  of  work  of  the  drag-line  exca- 
vator has  become  a  wide  one  since  1910.  Its  early  use  was  largely 
in  reclamation  work,  the  construction  of  ditches  and  dikes  on  irriga- 
tion and  drainage  projects.  Its  great  length  of  boom  gives  this 
excavator  a  wide  radius  of  operation  and  permits  of  the  deposition 
of  material  in  spoil  banks  at  a  sufficient  distance  from  the  sides  of 
the  cut  to  prevent  caving  of  the  banks.  The  drag-line  principle 
permits  the  excavation  of  material  at  a  considerable  depth  below 
the  surface  and  its  elevation  to  a  correspondingly  high  elevation 


Fig.  31.     Revolving  Excavator  on  Caterpillar  Tractor  Operating  on  Drainage  Work 

above  the  surface.    The  limitations  of  the  drag-line  excavator  are 
shown  in  Fig.  30. 

The  use  of  the  caterpillar  tractor  allows  a  heavy  machine  to 
move  over  soft,  wet  soils  on  drainage  work.  The  machine  starts  at 
the  lower  end  of  the  canal  and  excavates  as  it  moves  upstream,  thus 
allowing  the  surplus  soil  water  to  drain  off  through  the  new  channel. 
The  careful  operation  of  the  bucket  will  result  in  the  construction  of 
a  canal  with  smooth  and  uniform  bottom  and  side  slopes.  An 
example  of  this  class  of  earthwork  is  shown  in  Fig.  31.  Recent 
experience  in  the  South  and  West  has  proved  the  efficiency  of  this 
type  of  excavator  in  the  construction  of  dikes  and  earthen  dams  on 


355 


56 


EARTHWORK 


reclamation  projects  and  embankments  on  railroad  work.  The 
machine  moves  parallel  to  the  work  and  borrows  the  material  from 
one  side,  or  moves  ahead  of  the  work  and  borrows  the  material  from 
both  sides. 

Earthen  dams  and  dikes,  if  of  large  size,  should  be  made  in 
layers  of  about  6-  to  8-inch  depth,  and  each  layer  wetted  and  rolled 
by  a  heavy  steam  roller  before  the  deposition  of  the  material  for  the 
next  layer.  Small  dikes  and  railroad  fills  can  be  satisfactorily 
built  without  wetting  and  rolling.     The  drag-line  excavator  saves 


Fig.  32.     Drag-Line  Excavator  Operating  on  Placer  Mine  in  Siberia 

the  haulage  equipment  necessary  in  this  class  of  earthwork  where 
either  an  elevating  grader  or  a  power  shovel  is  used. 

The  scraper-bucket  excavator  is  very  efficient  in  the  excavation 
of  gravel  pits  and  in  stripping  soil  from  quarries  and  mines.  When 
the  power  shovel  has  become  drowned  out  of  a  pit  which  has  been 
Hooded,  the  drag-line  machine  can  work  from  a  higher  level  and 
excavate  for  a  considerable  distance  below  the  water.  Fig.  32 
shows  a  drag-line  excavator,  equipped  with  a  l|-yard  bucket  and  a 
65-foot  boom,  which  operated  successfully  in  1915  on  a  large  placer 
mine  in  eastern  Siberia.    Such  a  machine  has  proved  to  be  very 


356 


EARTHWORK 


57 


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357 


58  EARTHWORK 

economical  where  conditions  do  not  warrant  or  permit  the  use  of  a 
large  hydraulic  dredge. 

TEMPLET  EXCAVATOR 

Considerable  difficulty  has  been  experienced  in  the  maintenance 
of  drainage  and  irrigation  channels.  This  has  been  caused  by  their 
rapid  filHng  up  with  silt,  debris,  and  vegetable  growth.  Many  forms 
of  dredges  construct  the  channels  with  rough  bottoms,  uneven  sides^ 
and  steep  banks,  which  are  subject  to  subsequent  caving.  These 
irregularities  in  the  surfaces  of  the  channels  retard  the  flow  of  the 
water  and  augment  the  deposition  of  silt,  debris,  and  other  heavy 
materials  carried  by  the  water  in  suspension.    During  the  decade 


P^  ■:        '^t9f^KKK^^i^^^W^. .  :mmmmm'. .  5^H 

|BI 

-*■'— 

•  J^r- 

.. — — 1 

Fig.  34.     Narrow-Bottom  Templet  Excavator 
Courtesy  of  F.  C.  Austin  Drainage  Excavator  Company,  Chicago 

1905-1915,  a  unique  type  of  excavator,  called  the  templet  excavator, 
came  into  use  for  the  construction  of  open  ditches  with  true  and 
smooth  side  slopes  and  grades. 

Construction.  A  double-faced,  reversible,  positive-cleaning 
bucket  moves  along  a  guide  frame,  which  is  shaped  at  its  lower 
section  to  the  desired  cross-section  of  the  ditch.  The  guide  frame  is 
supported  on  a  platform  or  framework  composed  of  structural-steel 
members,  strongly  braced  and  bolted  together.  This  platform  is 
supported  on  wheel  trucks  or  caterpillar  tractors,  which  are  neces- 
sary for  soft,  wet  soils.  Templet  excavators  with  wide  and  with 
narrow  frames  are  shown  in  Figs.  33  and  34,  respectively. 

Power  Equipment.  Power  for  the  operation  of  the  machine 
may  be  furnished  by  a  steam-power  equipment  or  by  an  intemal- 

358 


EARTHWORK 


59 


combustion  engine.  The  latter  type  of  power  equipment  has  gener- 
ally been  found  to  give  very  satisfactory  results  and  to  be  cleaner, 
cheaper,  and  simpler  in  operation  than  the  ordinary  steam  plant. 
If  a  steam  engine  and  boiler  are  used,  a  25-horsepower  to  40-horse- 
power  engine  will  be  required,  while  a  gas  engine  for  the  same 
machine  should  have  from  50  horsepower  to  80  horsepower.  The 
power  plant  is  mounted  on  the  central  part  of  the  platform  and  is 
operated  with  a  set  of  levers  by  one  man. 

Excavating  Equipment.    The  excavating  equipment  consists  of 
the  guide  frame  and  the  bucket.    The  guide  frame  is  made  up  of  2 


-66'-0" 


Fig.  35.     Limitations  of  Templet  Excavator  with  Narrow-Bottom  Frame 
Courtesy  of  F.  C.  Austin  Drainage  Excavator  Company,  Chicago 

steel  members  which  are  placed  parallel  and  form  a  track  over  which 
the  bucket  moves.  This  frame  is  made  in  two  shapes  at  its  bottom 
section  to  provide  for  the  excavation  of  narrow  and  of  wide  ditches; 
the  side  slopes  are  nearly  1:1.  The  frame  is  well  braced  by  steel- 
frame  members  and  can  be  raised  and  lowered  through  the  platform. 

The  bucket  is  a  rectangular-shaped  box  with  2  open  ends  and 
cutting  edges.    A  plunger  head  fits  inside  the  box  section. 

Method  of  Operation.  The  guide  frame  is  lowered  to  the  ground 
surface  and  the  bucket  drawn  down  and  along  the  bottom  of  the 
frame.    As  it  moves  along  it  cuts  a  thin  slice  of  earth  which  is 


359 


60 


EARTHWORK 


carried  on  to  the  upper  section  of  the  frame.  Here  trips  are  located 
and  they  push  the  plunger  head  through  the  bucket  and  thus  the 
contents  are  discharged  into  either  wagons  or  cars  or  upon  a  spoil 
bank  below.  As  the  bucket  moves  back  and  forth  along  the  frame, 
the  latter  is  lowered  so  as  to  gradually  feed  the  bucket  into  the 
earth  and  increase  the  depth  of  cut.  Thus  a  section  of  ditch  prism 
about  3J  feet  in  length  is  made  with  one  position  of  the  machine. 
The  machine  then  moves  ahead  and  cuts  another  section  of  ditch, 


Fig.  36.     Limitations  of  Templet  Excavator  with  Wide-Bottom  Frame 
Courtesy  of  F.  C,  Austin  Drainage  Excavator  Company,  Chicago 

and  so  on.    The  limitations  of  the  two  types  of  templets — narrow 
and  broad  bottoms — are  given  in  Figs.  35  and  36. 

Cost  of  Operation,  The  gasoline-power  machine  equipped  with 
caterpillar  tractors  is  the  type  of  templet  excavator,  which  is  most 
generally  used  in  the  excavation  of  channels  in  loose  and  soft  soils. 
For  the  operation  of  this  machine  a  crew  of  3  to  4  men  would  be 
required;  an  engineer,  an  assistant,  a  laborer,  and  a  teamster.  A 
steam-operated  machine,  run  on  a  track  would  require  the  services 
of  one  or  two  extra  men  to  haul  fuel,  move  track,  etc.  The  engineer 
operates  the  bank  of  levers  which  control  the  movement  of  the 


360 


EARTHWORK  61 

bucket,  the  raising  and  lowering  of  the  frame,  and  the  tractive  move- 
ment of  the  machine  along  the  surface.  The  assistant  keeps  the 
machinery  oiled  and  in  good  working  order.  The  laborer  provides 
planking  or  tracking  w^here  necessary,  and  does  general  service  about 
the  machine.  The  teamster  hauls  the  gasoline,  water,  and  supplies 
necessary  for  the  work. 

Illustrative  Example.  The  cost  of  operation  of  a  typical  machine 
in  the  construction  of  a  drainage  channel  through  alluvial  soil  under 
favorable  conditions  would  average  about  as  follows  for  a  10-hour 
day: 

Operating  Cost  of  Templet  Excavator 
Labor: 

1  engineer  $4.00 

1  assistant  2.50 

1  laborer  '  2.00 

1  team  and  driver  3 .  50 

Total  labor  cost,  per  day  $12 .  00 

Fuel  and  Supplies: 

35  gallons  of  gasoline,  @  20c 
Oil,  waste,  etc. 

Total  fuel  and  supplies  $8.00 

General  and  Overhead  Expenses: 

Depreciation  (12 1%  of  $12,000)* 
Interest  (6%  of  $12,000)* 
Repairs  and  incidentals 

Total  general  and  overhead  expense  $19.00 

Total  Cost  of  Operation  for  10-hour  Day  $39.00 

Total  Excavation  (cu.  yd.)  700 

Unit  Cost  of  Templet  Excavating,  per  cu.  yd.,  $39.00-5-700=  00.055 

Field  of  Usefulness.  A  water  channel,  to  secure  highest  effi- 
ciency of  operation,  should  have  a  true  grade  and  uniform  and 
smooth  side  slopes.  On  irrigation  and  drainage  projects,  the  dis- 
tribution canals  and  open  ditches  are  peculiarly  susceptible  to  filling 
up  with  silt,  debris,  and  vegetable  matter  during  seasons  of  low  flow. 
In  the  case  of  small  ditches,  this  filling  up  may  become  so  great  in  a 
few  years  as  to  render  the  channel  practically  useless.  This  means 
that  these  artificial  waterways  must  be  cleaned  out  every  few  years 
in  order  to  maintain  their  efficiency  and  capacity.     In  order  to 

*  Based  on  150  working  days  a  year  and  an  8-year  life. 

361 


$7.00 
1.00 

$10.00 
4.80 
4.20 

62  EARTHWORK 

reduce  this  maintenance  expense  to  a  minimum,  it  is  advisable  to 
construct  the  channels  as  nearly  mechanically  perfect  as  possible. 
The  templet  excavator  is  the  best  form  of  excavator  for  the 
construction  of  an  open  channel,  where  the  soil  conditions  are  favor- 
able. In  alluvial  soils,  such  as  loam,  clay,  sandy  loam,  and  marl, 
the  machine  does  very  satisfactory  work.  But  in  hard  soils,  such 
as  hard  pan  or  indurated  gravel,  and  in  lands  where  many  obstruc- 
tions such  as  stumps,  boulders,  and  roots  occur,  the  progress  is  slow 
and  difficult  and  the  work  expensive. 

WHEEL  EXCAVATOR 

The  wheel  excavator  is  a  machine  which  has  been  devised  to 
excavate  small  open  ditches  on  reclamation  work.    Most  types  of 


Fig.  37.     Wheel  Excavator  Constructing  Small  Drainage  Ditch 

excavators  are  unfitted  on  account  of  size  and  method  of  operation 
to  construct  the  smaller  lateral  ditches  of  drainage  and  irrigation 
systems,  and  there  has  been  a  great  demand,  beginning  in  the 
decade  of  1905-1915,  for  a  small,  hght,  portable  machine,  which  can 
excavate  to  a  true  and  uniform  cross-section. 

Construction.  The  ditcher  consists  of  a  frame  which  supports 
the  power  equipment  on  the  front  end,  and  a  pivoted  framework 
containing  the  excavating  wheel  on  the  rear  end.  The  platform  is 
supported  at  the  front  on  an  axle  which  has  2  broad-tired  steel  wheels, 
and  at  the  rear  by  2  caterpillar  tractors,  which  allow  the  machine 
to  operate  in  wet,  soft  soils.  A  view  of  a  wheel  excavator  con- 
structing a  small  drainage  channel  is  shown  in  Fig.  37. 

362 


EARTHWORK 


63 


Power  Equipment.  The  power  may  be  supplied  either  by  a 
steam  or  internal-combustion  engine.  The  earlier  machines  were 
supplied  with  the  former  type  of  engine  but  the  more  recent  machines 
are  nearly  all  equipped  with  gasoline  engines.  These  gasoline 
engines  are  generally  of  the  marine  type  and  made  with  4-cycle 
multiple  cylinders,  ranging  from  20  horsepower  to  90  horsepower. 
They  are  provided  with  high-tension  magneto  and  dual  ignition. 

The  motive  power  is  transmitted  to  the  wheels  either  by  sprocket 
chain  or  bevel-gear  drive. 

Excavating  Equipment.  The  excavating  equipment  consists  of 
the  excavating  wheel  and  belt  conveyor.  The  wheel  is  an  open  steel 
frame,  around  the  periphery  of  which  are  attached  from  8  to  12 


Fig.  38.     Diagram  of  General  Dimensions  and  Specifications  of  Wheel  Excavators 

buckets  of  scoop  shape.  At  the  rear  and  near  the  upper  part  of  the 
wheel  is  placed  the  belt  conveyor,  which  projects  out  a  considerable 
distance  either  side  of  the  machine. 

Method  of  Operation.  The  excavating  wheel  revolves  either 
on  a  central  axle  or  anti-friction  wheels  placed  along  its  rim  and 
each  bucket  cuts  out  a  thin  slice  of  earth  which  is  deposited  on  the 
machine  end  of  the  belt  conveyor,  when  the  bucket  reaches  the  top 
of  the  wheel.  The  operator  gradually  feeds  the  wheel  into  the 
ground  as  the  wheel  revolves.  After  one  section  has  been  dug  to 
the  required  depth,  the  machine  moves  ahead  several  feet  under  its 
own  power  and  another  section  is  dug,  and  so  on.  The  sizes,  limita- 
tions, and  capacities  of  the  various  sizes  of  a  well-known  make  of 
wheel  excavator  are  given  in  Fig.  38  and  Table  V, 


363 


64 


EARTHWORK 


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364 


EARTHWORK  65 

Cost  of  Operation.  The  cost  of  operation  depends  on  the  size 
of  the  job,  the  size  and  make  of  excavator,  the  character  and  condi- 
tion of  the  soil,  the  efficiency  of  the  operator,  etc. 

Ilhistratire  Example.  With  a  machine  which  digs  a  ditch  with 
a  top  width  of  4  feet  6  inches,  an  average  depth  of  3  feet  6  inches, 
bottom  width  rounded  to  12  inches,  and  side  slopes  of  about  ^il, 
the  average  cost  of  operation  for  a  10-hour  day  would  be  about  as 
follows : 

Operating  Cost  of  Wheel  Excavator 

Labor: 


1  operator,  @  $125  per  month 

$4.00 

1  assistant 

2.50 

1  laborer,  @  $2.00 

2.00 

1  team  and  driver 

3.50 

Total  labor  cost,  per  day 

$12.00 

Fuel  and  Supplies: 

30  gallons  gasoline,  @  20c 

$6.00 

Oil,  waste,  and  supplies 

1.00 

Total  fuel  and  supplies 

$7.00 

General  and  Overhead  Charges: 

Depreciation  (12|%  of  $6000)* 

$5.00 

Interest  (6%  of  $6000)* 

2.40 

Repairs  and  incidentals 

4.60 

Total  general  and  overhead  expense 

$12.00 

Total  Operating  Cost  per  10-hour  Day  $31.00 

Average  Progress  per  Day  (ft.)  2000 

Average  Daily  Excavation  (cu.  yd.)  700 

Unit  Cost  of  Wheel  Excavating,  per  cu.  yd.,  $31.00^700=  00.044 

Field  of  Usefulness.  The  wheel  excavator  is  the  most  practical 
form  of  excavator  for  small  ditches  where  the  soil  conditions  are 
favorable.  This  machine  cannot  excavate  economically  very  hard, 
dense  soils,  or  where  large  quantities  of  stumps,  boulders,  and  other 
obstructions  are  present.  In  glacial  clay,  alluvium,  marl,  and 
similar  soils,  this  excavator  operates  very  smoothly  and  satisfactorily. 

In  irrigation  and  drainage  systems,  where  the  smaller  ditches 
run  full  only  a  small  part  of  each  year,  a  large  amount  of  silt,  debris, 
and  vegetation  gradually  accumulates.  These  obstructions  in  the 
course  of  a  few  years  will  gradually  fill  up  and  greatly  reduce  the 

*  Based  on  150  working  days  a  year  and  an  8-year  life. 

365 


66 


EARTHWORK 


carrying  capacity  of  the  channels.  Hence  it  is  necessary  to  con- 
struct the  smaller  channels  to  as  near  true  grade  and  cross-section  as 
is  practicable.  In  open,  porous  soils,  such  as  occur  often  on  irriga- 
tion projects,  it  becomes  necessary  to  line  the  ditches  with  some 


Fig.  39.     Tower  Excavator  Operating  on  New  York  State  Barge  Canal 

impervious  material  such  as  concrete  to  prevent  large  seepage  losses. 
In  such  cases  it  is  a  great  advantage  to  excavate  a  channel,  which 
is  to  be  subsequently  lined,  with  a  true  grade  and  smooth  side  slopes, 
so  that  the  form  work  for  the  concrete  may  be  set  without  the  extra 
labor  and  expense  of  trimming  and  shaping  the  excavation. 


EARTHWORK  67 

TOWER  EXCAVATOR 

The  tower  excavator  is  a  unique  type  of  machine  which  was 
developed  and  used  with  success  several  years  ago  on  the  Chicago 
Drainage  Canal  and  recently  on  the  construction  of  the  New  York 
State  Barge  Canal.  As  will  be  seen  from  Fig.  39,  this  excavator 
derives  its  name  from  its  principal  part,  which  is  a  movable  tower. 

Construction.  The  tower  is  a  framed,  timber  structure,  the 
height  of  which  is  determined  by  the  width  of  the  area  to  be  exca- 
vated. The  tower  rests  on  a  platform  or  car,  which  is  braced 
by  overhead,  horizontal-chord,  combination  trusses.  This  car  is 
mounted  on  4  solid,  double-flanged  cast-steel  wheels  generally  about 
14  inches  to  16  inches  in  diameter  and  with  4-inch  treads.  The 
wheels  run  on  a  track,  which  consists  of  80-pound  to  90-pound  rails, 
spiked  to  cross  ties,  w^hich  are  bolted  to  30-foot  planks.  The  car 
and  tower  are  moved  ahead  by  a  cable  which  passes  over  a  sheave 
on  the  car  and  thence  to  a  "deadman"  or  anchorage  placed  at  a  suit- 
able point  ahead  of  the  car,  and  then  back  to  a  drum  on  the  engine. 
The  tower  is  braced  to  the  car  by  cables  which  extend  from  the  top 
of  the  tower  to  the  rear  corners  of  the  car. 

Power  Equipment.  The  power  equipment  is  placed  on  the  rear 
of  the  car  and  consists  of  a  vertical  boiler  and  a  double-drum  hoist- 
ing engine.  The  engine  is  usually  of  the  vertical,  reversible  type, 
with  double,  40-inch  by  12-inch  cylinders,  and  equipped  with 
friction-clutch  control  for  the  drums. 

Excavating  Equipment.  The  excavating  equipment  consists 
essentially  of  a  2-line  scraper  bucket.  At  the  rear  of  the  bucket  is  a 
frame  carrying  2  sheaves  at  right  angles  to  the  cutting  edge,  which 
is  strongly  reinforced  and  provided  mth  teeth  for  the  excavation  of 
hard  material.  On  the  bottom  of  the  bucket  are  attached  2  curved 
shims,  or  shoes.  The  front  of  the  bucket  is  connected  to  the  drag- 
line drum  of  the  engine  by  a  cable  which  passes  over  a  sheave  sus~ 
pended  on  the  front  side  of  the  tower  about  J  of  its  height  from  the 
base.  Another  cable  extends  from  the  hoisting  drum  of  the  engine 
over  a  sheave  at  the  top  of  the  tower,  then  between  the  sheaves  on 
the  bail  of  the  bucket  and  then  to  an  anchorage  at  the  far  side  of  the 
excavation. 

Method  of  Operation.  The  bucket  is  lowered  over  the  hoist 
line  by  allowing  it  to  slide  down  the  cable  by  its  own  weight,  to  the 

367 


68 


EARTHWORK 


far  side  of  the  cut.  Then  the  bucket  is  loaded  by  pulHng  it  toward 
the  tower  by  winding  up  the  drag-hne  cable.  When  the  spoil  bank 
is  reached,  the  hoisting  cable  is  raised  and  the  bucket  is  overturned 
and  dumped.  The  bucket  is  returned  to  the  excavation  by  still 
further  tightening  the  hoisting  cable  and  releasing  the  drag-line 
cable,  whereby  the  bucket  rises  and  slides  back  to  the  starting 
point.  Where  a  tower  65  feet  in  height  has  been  used,  a  reach  of 
210  feet  from  the  far  side  of  the  excavation  to  the  near  side  of  the 
spoil  bank  was  attained  with  efficiency  of  operation.     A  bucket,  of 


Tower  lio.S 
ELEV/iTIOti 
Fig.  40.     Diagram  of  Double-Tower  Excavator 


2-cubic  yard  capacity,  made  an  average  output  of  3  cubic  yards  and 
was  operated  at  the  rate  of  4  cubic  yards  per  minute. 

A  crew  of  from  5  to  9  men  is  required  to  operate  a  tower  exca- 
vator, depending  on  the  magnitude  of  the  job,  the  character  of  the 
material  to  be  excavated,  etc.  Under  average  conditions,  there  will 
be  required  an  operator,  a  fireman,  a  team  and  driver,  and  3 
laborers.  The  operator  is  stationed  on  a  platform  on  the  rear  side 
of  the  tower  and  at  about  \  its  height.  He  controls  the  machinery 
by  a  set  of  levers  and  brakes  and  has  an  unobstructed  view  of  the 
work.  The  fireman  keeps  the  boiler  and  machinery  supplied  with 
fuel,  water,  and  oil,  and  in  proper  working  condition.    The  team  and 


368 


EARTHWORK  69 

driver  haul  fuel,  water,  and  supplies  to  the  work.     The  laborers 
move  the  track  and  perform  general  service  about  the  work. 

DoubIe=Tower  Excavator.  A  double-tower  excavator  was  used 
some  years  ago  on  a  section  of  the  Chicago  Drainage  Canal.  A 
diagrammatic  view  of  this  excavator  is  shown  in  Fig.  40.  As  will  be 
noted  from  the  plan,  the  inclined  booms  were  so  designed  that  a 
straight  line  from  the  apex  of  either  tower  to  the  point  of  the  oppo- 
site boom,  clears  the  side  of  the  tower.  This  allowed  each  bucket 
to  clear  the  tower  and  empty  directly  on  the  adjacent  spoil 
bank. 

A  double-drum  hoisting  engine  was  located  on  the  side  of  the 
platform  of  each  tower.  Each  bucket  was  operated  by  a  drag  line 
and  a  hoisting  line.  The  buckets  were  loaded,  dumped,  and  returned 
to  the  excavation  as  is  described  above  for  the  single  tower  excavator. 
By  changing  the  location  of  the  suspended  sheaves,  the  position  of 
the  bucket  in  digging  was  altered  so  as  to  reach  the  entire  half  width 
of  the  canal  prism.  This  machine,  in  the  excavation  of  a  canal 
section  having  a  bottom  width  of  26  feet,  side  slopes  of  2:1,  and  an 
average  depth  of  27  feet,  through  a  clay  soil,  did  very  satisfactory 
work. 

Cost  of  Operation.  Illustrative  Example,  The  following  may 
be  taken  as  an  estimate  of  the  cost  of  operation  of  a  single-tower 
excavator,  equipped  with  a  75-foot  tower,  controlHng  a  250-foot 
width  of  excavation,  a  2-yard  scraper  bucket,  and  a  10  X  12-inch 
double-drum,  vertical  hoisting  engine.  The  excavated  material  would 
be  dumped  upon  a  spoil  bank  at  the  tower  side  of  the  excavation 
and  into  wagons  or  dump  cars  by  means  of  a  loading  platform.  A 
train  of  four  5-yard  dump  cars  would  be  loaded  in  about  15  minutes. 
An  average  output  of  600  cubic  yards  would  be  attained  in  the 
excavation  of  a  glacial  clay  under  average  working  conditions  during 
a  10-hour  working  day: 


Labor: 


Operating  Cost  of  Single-Tower  Excavator 

1  engineer  $4.00 

1  fireman  2.50 

1  team  and  driver  3 .  50 

3  laborers,  @  $2.00  each  6 .  00 


Total  labor  cost,  per  day  $16.00 


.S6» 


70                                     EARTHWORK 

Fuel  and  Supplies: 

I  ton  of  coal,  @  $4.00 

$3.50 

Oil,  and  waste 

0.50 

Total  fuel  and  supplies 

$4.00 

General  and  Overhead  Expenses: 

Depreciation,  (10%  on  $2000)* 

$1.40 

Interest  (6%  of  $2000)* 

0.80 

Repairs,  and  incidentals 

5.50 

Total  general  expense 

$7.70 

Total  Cost  of  Operation  for  10-hr.  Day  $27 .  70 

Average  Excavation  per  10-hr.  Day  (cu.  yd.)  600 

Unit  Cost  of  Single-Tower  Excavating,  per  cu.  yd.,  $27.70 -J- 600  =     00 .  046 

Field  of  Usefulness.  The  tower  excavator  was  originally  used 
in  canal  excavation  where  the  cross-section  was  very  wide  with  a 
comparatively  shallow  depth.  When  the  top  width  of  a  channel  is 
over  80  feet,  it  becomes  necessary  to  use  drag-line  excavators  in 
pairs,  one  along  each  bank,  or  a  floating  dipper  dredge  which  shifts 
from  one  side  of  the  channel  to  the  other.  The  tower  excavator 
can  cut  the  full  width  of  the  channel  at  one  set-up  and  complete  the 
section  as  it  moves  along.  This  type  of  excavator  could  not  be 
used  satisfactorily  in  very  wet  soils,  or  where  rock  occurred  in  great 
quantity. 

The  tower  excavator  is  especially  efficient  in  the  excavation  of 
large,  shallow  areas  such  as  reservoirs,  athletic  fields,  and  the  base- 
ments of  large  buildings.  In  such  cases,  it  might  be  advisable  to 
have  the  tower  or  towers  move  over  curved  tracks;  the  center  of 
curvature  being  the  point  of  anchorage  of  the  hoist  cable. 

Quarries,  surface  mines,  and  gravel  pits  can  be  economically 
stripped  with  a  tower  excavator,  when  the  area  covered  is  sufficient 
to  warrant  the  installation  of  the  plant  and  the  soil  conditions  are 
favorable  to  uniform  scraper-bucket  operation. 

WALKING  SCOOP  DREDGES 

The  walking  dredge  is  rather  a  novelty  in  the  field  of  excavating 
machinery  and  derives  its  name  from  its  ability  to  move  over  the 
ground  under  its  own  power  and  to  turn  short  angles  or  curves  with- 
out sliding  or  skidding.  The  walking  scoop  type  was  devised  about 
1905,  and  is  similar  in  general  construction  and  operation  to  the 

♦Based  on  a  10-year  life  and  150  working  days  per  year. 

870 


EARTHWORK 


71 


floating  dipper  dredge.  Another  type,  placed  on  the  market  in 
1914,  is  an  adaptation  of  the  "walking"  principle  to  the  drag-Hne 
excavator  and  will  be  discussed  later. 

Construction.  The  walking  scoop  dredge  consists  essentially 
of  a  wooden  hull  supported  on  6  legs  or  feet  and  supporting  the 
operating  machinery  and  excavating  equipment.  The  hull  is  con- 
structed of  heavy  timbers  and  is  braced  longitudinally  by  large, 
overhead,  wooden  trusses.  It  is  usually  made  of  sufficient  width  to 
straddle  the  ditch  which  it  is  excavating.  On  the  front  of  the  hull 
is  placed  the  A-frame,  which  consists  of  two  heavy  timbers,  bolted 
to  the  sides  of  the  hull  at  their  lower  ends  and  joined  at  the  upper 
ends  to  a  "head"  casting.     The  A-frame  sets  in  nearly  a  vertical 


Fig.  41.     General  View  of  Walking  Scoop  Dredge 

plane  and  is  braced  to  the  rear  corners  of  the  hull  by  wire  cables 
which  extend  to  the  top  of  the  frame. 

Operating  Equipment.  The  operating  equipment  for  steam 
power  is  similar  to  that  used  for  a  floating  dipper  dredge.  The 
boiler  is  placed  at  the  rear  of  the  hull,  and  in  front  of  it  are  the 
hoisting  and  swinging  engines.  These  will  be  fully  discussed  in  the 
section  entitled  "Floating  Dipper  Dredges". 

On  several  jobs,  it  has  been  found  to  be  more  economical  to  use 
a  gasoline  engine  instead  of  the  steam  equipment.  Engines  of  the 
multiple-cylinder  marine  type  are  generally  used  and  vary  from  16 
horsepower  to  50  horsepower,  depending  on  the  capacity  of  the  exca- 
vator, the  size  of  the  ditch,  and  the  character  of  the  soil.    A  machine 


371 


72 


EARTHWORK 


with  a  40-foot  boom  and  a  f-yard  dipper  has  been  satisfactorily 
operated  by  a  50-horsepower  engine. 

Walking  Equipment.  The  hull  is  supported  at  each  of  its  cor- 
ners by  a  timber  platform  shaped  like  a  large  stone  boat.  Each 
"foot"  is  about  6  feet  wide,  8  feet  long,  and  4  inches  thick,  and  has  an 
iron  rod  bolted  across  the  bottom  near  the  front  edge  to  prevent 
slipping.  Each  pair  of  feet  is  connected  by  a  timber  so  that  the 
two  feet  will  move  conjointly.  Each  foot  is  pivoted  to  the  hull  and 
connected  to  a  drum  of  the  swinging  engine  by  a  chain,  so  that  the 
feet  may  be  turned  by  the  revolution  of  the  drum.     In  the  center 

of  each  side  or  midway  between 
the  corner  feet  is  a  center  foot 
similar  in  construction  to  the  corner 
feet.  On  the  under  side  of  each 
center  foot,  a  transverse  6-inch  by 
6-inch  timber  is  bolted  to  prevent 
sliding  or  slewing.  A  large  timber 
extends  from  the  top  of  each  center 
foot,  between  each  pair  of  trusses, 
where  it  is  pivoted.  A  chain,  one 
end  of  which  is  fastened  to  the  side 
timbers  of  the  hull,  passes  over  two 
pulleys  attached  to  the  frame  on 
which  the  foot  support  is  pivoted, 
and  then  passes  along  the  hull  to  the 
rear  corner  and  across  the  back  end 
to  a  drum  near  the  center  of  the  hull. 
The  movement  of  the  excavator  is  effected  as  follows:  The 
drum  is  revolved  and  the  chain  pulls  the  foot  support  gradually  to 
a  vertical  position.  This  raises  the  dredge  from  its  corner  feet  and 
shoves  it  ahead  about  6  feet.  The  rear  chain  is  then  released  and 
the  weight  taken  off  the  center  feet,  which  are  pulled  ahead  by  a 
chain  attached  to  a  drum,  located  near  the  front  part  of  the  hull. 
A  general  view  of  a  walking  scoop  dredge  is  shown  in  Fig.  41. 

Excavating  Equipment.  The  excavating  equipment  consists  of 
the  boom,  dipper  handle,  and  dipper,  all  of  which  are  of  unusual 
design  in  this  machine. 

The  boom  is  made  up  of  two  parts;  the  upper  part  is  supported 


Fig.  42.     Dipper  and  Dipper  Handle 
of  Walking  Scoop  Dredge 


372 


EARTHWORK  73 

at  its  lower  end  on  a  turntable,  similar  to  those  used  on  a  floating 
dipper  dredge.  The  upper  end  is  supported  by  a  cable  from  the 
peak  of  the  A-frame.  The  lower  part  of  the  boom  is  pivoted  at  one 
end  to  the  lower  end  of  the  upper  section  and  on  its  outer  end  is 
pivoted  an  iron-trussed  framework  shaped  like  a  walking  beam. 
This  framework  is  the  dipper  handle,  to  the  lower  end  of  which  is 
attached  the  dipper  which  is  shaped  like  a  slip  scraper.  The  dipper 
and  dipper  handle  are  shown  in  Fig.  42. 

A  chain  or  cable  passes  from  the  upper  end  of  the  handle  to  a 
drum  on  the  hull.  By  winding  up  this  chain  or  cable,  the  top  of 
the  frame  is  pulled  back.  A  chain  or  cable  is  also  fastened  to  the 
lower  end  of  the  handle  at  the  back  of  the  scoop.  This  line  passes 
over  sheaves  in  the  outer  ends  of  the  booms  and  thence  to  a  drum 
on  the  hull.  The  method  of  excavation  is  as  follows:  The  lower 
section  of  the  boom  is  lowered  until  the  tip  of  the  scoop  is  at  the 
required  elevation;  the  Hue  attached  to  the  upper  end  of  the  dipper 
handle  is  drawn  in  by  revolving  the  drum,  and  the  scoop  is  thus 
forced  into  the  earth.  After  the  scoop  is  filled,  the  lower  section  of 
the  boom  is  raised  and  simultaneously  the  whole  boom  is  swung 
to  one  side  until  the  scoop  is  over  the  spoil  bank,  when  the 
upper  line  is  released  and  the  lower  line  is  drawn  in  until  the 
scoop  is  pulled  back  to  the  boom  and  the  contents  of  the  scoop  are 
dumped. 

The  walking  scoop  dredge  can  move  across  fairly  level  land  at 
the  rate  of  about  1  mile  in  a  10-hour  day.  It  can  make  a  quarter 
turn  in  about  50  feet.  It  may  be  operated  as  a  rear  or  head-on 
excavator.  In  the  first  case,  the  machine  starts  at  the  outlet  and 
works  upstream,  backing  away  from  the  excavation  similar  to  the 
drag-line  excavator,  w^hile  in  the  latter  case,  the  machine  starts  at 
the  upper  end  of  the  channel  and  straddles  it  as  it  works  downstream. 

WALKING  DRAQ=LINE  EXCAVATOR 

This  machine  is  an  adaptation  of  a  walking  traction  device  to 
the  drag-line  excavator.  The  advantages  of  this  method  of  traction 
over  the  ordinary  ones  of  rollers,  wheels,  or  caterpillars,  are  the  pro- 
duction of  a  direct  bearing  pressure  on  the  soil  and  the  elimination 
of  track,  plankways,  skids,  and  the  labor  necessary  for  their  manipu- 
lation. 


373 


74 


EARTHWORK 


Construction.  The  walking  drag-line  excavator  differs  from  the 
ordinary  drag-line  machine  principally  in  its  substructure  construc- 
tion. The  customary  lower  frame  and  truck  rollers  or  caterpillar 
tractors  are  replaced  by  the  w^alking  device,  which  is  quite  different 
in  design  and  operation  from  that  described  above  for  the  walking 
scoop  dredge. 

The  superstructure  of  this  excavator  is  very  similar  in  design 
and  construction  to  the  ordinary  drag-line  excavator.  Three  sizes 
of  machine  are  in  regular  use :  the  smallest,  equipped  with  a  40-foot 
boom,  a  1-yard  bucket,  and  operated  by  a  45-horsepower  kerosene 


Fig.  43.    Walking  Drag-Line  Excavator 

Courtesy  of  Monighan  Machine  Company 

engine;  the  medium,  equipped  with  a  50-foot  boom,  a  2-yard 
bucket,  and  operated  by  a  steam  plant;  and  the  largest,  provided 
with  a  60-foot  boom,  a  2J-yard  or  3-yard  bucket,  and  operated  by  a 
steam  plant. 

Walking  Equipment.  The  walking  device  consists  of  two  large 
shoes  or  platforms,  one  on  each  side  of  the  central  circular  support, 
and  two  wheel  segments  or  cams,  each  of  which  is  keyed  to  the  end 
of  a  heavy  shaft  extending  across  the  machine.  On  the  lower  end 
of  each  cam  is  pivoted  a  beam  whose  ends  are  chain-connected  to 
the  ends  of  each  platform.    A  view  of  this  mechanism  is  shown  in 


374 


EARTHWORK  75 

Fig.  43.  A  large  gear  wheel  on  the  shaft  meshes  with  a  pinion  on 
the  loading-drum  shaft  of  the  main  engine.  The  pinion  is  controlled 
by  a  jaw  clutch  and  brake. 

To  move  the  machine,  the  pinion  clutch  is  thrown  in  and  the 
engine  started.  As  the  shaft  revolves,  the  cams  and  pivoted  beams 
lift  the  platforms  and  swing  them  forward  to  a  resting  place  on  the 
ground.  As  the  shaft  revolves,  the  cams  move  over  the  upper  sur- 
faces of  the  platforms  until  they  come  into  contact  with  the  stop 
blocks,  when  the  motion  is  stopped,  and  the  machine  is  moved  for- 
ward and  downward  to  the  surface.  When  further  movement  is  not 
desired,  the  cams  are  revolved  until  the  beams  and  platforms  are 
elevated  above  the  ground,  and  the  machine  then  rests  entirely  on 
its  circular  base,  about  which  it  may  revolve  as  a  pivot  for  the  pur- 
pose of  excavating.  The  pinion  is  now  locked  by  a  brake  and  the 
drum  clutch  released  to  commence  digging. 

Field  of  Usefulness.  The  walking  excavator  is  especially 
adapted  to  use  oh  drainage  and  irrigation  projects,  where  several 
ditches  are  to  be  built  in  one  locality.  Ordinarily,  when  an  excavator 
is  through  with  one  job  and  is  ready  to  commence  another  channel, 
it  is  generally  necessary  to  dismantle  the  machine,  transport  the 
parts  to  the  new  site,  and  reassemble  them.  This  involves  a  con- 
siderable expenditure  of  time,  labor,  and  money.  The  walking 
machine  can  move  over  soft,  wet,  and  rough  ground  and  can  make 
sharp  turns  by  revolving  about  the  central  support.  The  machine 
can  be  erected  at  the  transportation  point  where  it  is  unloaded  from 
cars  or  boats  and  can  walk  to  the  job  at  the  rate  of  about  3  miles 
per  10-hour  day. 

This  excavator  can  be  efficiently  used  in  the  excavation  of  wide 
ditches  by  moving  along  the  center  of  the  channel  and  working 
alternately  on  opposite  sides. 

The  walking  scoop  dredge  operates  at  about  the  same  cost  as 
the  floating  dipper  dredge.  A  machine  equipped  with  a  l|-cubic 
yard  dipper,  and  operated  by  a  40-horsepower  gasoline  engine,  can 
handle  about  1500  cubic  yards  of  loam  and  clay  per  10-hour  day, 
at  an  average  cost  of  about  4  cents  per  cubic  yard. 


375 


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EARTHWORK 

PART  II 


DRE  DQ  ES— (Continued) 

FLOATING  EXCAVATORS 

Classification.  The  excavators  of  this  division,  as  the  name 
indicates,  move  over  the  water  Hke  a  boat.  They  may  be  classified 
as  to  the  method  of  operation  as  follows:  the  dipper  dredge,  the 
ladder  dredge,  and  the  hydraulic  dredge. 

DIPPER  DREDGE 

Dipper  dredges  may  be  classified  as  to  the  field  of  operation 
3B  follows:  dredges  for  the  excavation  of  drainage  and  irrigation 
channels,  dredges  with  narrow  hulls  and  side  floats  for  digging 
and  maintaining  canals,  and  marine  dredges  for  river  and  harbor 
improvements.  These  three  classes  comprise  many  types  and  sizes 
of  dredges  depending  upon  the  service  for  which  the  machines  are 
intended.  The  general  arrangement  and  method  of  operation  of 
all  the  types  are  very  similar. 

Construction.  The  principal  parts  of  a  dipper  dredge  a^e  the 
hull,  the  power  equipment,  and  the  excavating  equipment.  The 
chief  differences  in  the  construction  of  the  different  types  of  dredge 
are  in  the  design  of  the  machinery,  boom  operation,  and  kind 
of  spuds  used.  Detailed  views  of  dipper  dredges  equipped  with 
bank  spuds  and  with  vertical  spuds  are  shown  in  Figs.  44  and  45, 
respectively. 

Hull.  The  hull  or  boat  may  be  constructed  of  either  w^ood 
or  steel.  For  marine  dredges,  where  the  machine  is  to  be  kept  in 
use  over  long  periods  of  time  and  where  the  cost  of  maintenance  is 
an  important  item,  steel  hulls  are  desirable.  For  inland  operation, 
as  on  reclamation  work,  wooden  hulls  are  preferable  on  account  of 
availability  and  economy  of  material  and  the  ease  of  assembly 
and  dismantling. 

377 


78 


EARTHWORK 


378 


EARTHWORK 


79 


The  dimensions  of  the  hull  depend  upon  the  size  of  the 
machinery,  length  of  boom,  capacity  of  dipper,  and  width  of  channel. 
In  the  construction  of  small-sized  channels,  the  width  of  the  hull 
should  be  nearly  the  width  of  the  channel  so  as  to  secure  the  increased 
stability  afforded  by  the  use  of  bank  spuds.  The  width  of  the  hull 
should  bear  some  relation  to  the  length  of  the  boom,  as  the  tendency 
of  the  dredge  to  tip  sidewise  will  depend  upon  the  distance  of  the 
dipper  from  the  center  of  the  hull.  The  length  of  the  hull  must 
be  sufficient  to  provide  adequate  space  for  the  housing  of  the  operat- 
ing equipment*  but  principally  must  be  proportioned  to  balance 
the  weight  of  the  excavating  equipment  in  its  various  positions. 
The  depth  of  the  hull  is  governed  by  the  necessary  displacement, 


Fig.  45.     Ditching  Dredge  with  Vertical  Spuds.     Letters  Have  Same  Significance 
as  in  Fig.  44 

but  ordinarily  should  be  made  with  as  light  draft  as  possible  to 
provide  for  shallow  excavation. 

The  wooden  hull  is  generally  made  up  of  heavy  timbers,  strongly 
braced  transversely  and  longitudinally  to  form  a  rigid  and  strong 
box.  All  the  outside  joints  are  calked  with  oakum  and  tar  to  make 
the  hull  water-tight. 

Operating  Equipment.  The  operating  equipment  is  of  the 
same  general  design  in  all  types  of  dipper  dredges.  The  essential 
parts  are  the  boiler,  the  hoisting  and  backing  machinery,  the  swinging 
machinery,  and  the  spud  machinery.  An  interior  view  of  a  dipper 
dredge,  showing  the  operating  equipment,  is  given  in  Fig.  46. 

The  locomotive  type  of  boiler  is  generally  used  on  account  of 
its  adaptability  to  various  kinds  and  grades  of  fuel  and  its  ease 


379 


80 


EARTHWORK 


of  cleaning.  The  Scotch  marine  type  is  used  on  the  smaller  sizes 
of  dredge  and  under  favorable  working  conditions  is  perhaps  more 
economical  of  fuel,  more  durable,  and  safer  than  the  locomotive 
type,  but  under  the  usual  conditions  of  poor  fuel,  hard  water,  and 
severe  loading,  the  latter  generally  renders  the  more  efficient  and 
economical  service.  A  working  pressure  of  125  pounds  is  generally 
used  for  the  operation  of  the  dredge.  A  feed-water  heater  should 
be  used  to  soften  and  purify  the  boiler  water  in  localities  where 
hard  or  alkali  water  exists.    A  duplex  pump  and  injector  supply 


Fig.  46.     Interior  of  Dipper  Dredge  Showing  Operating  Equipment 

the  feed  water  to  the  boiler.    The  water  may  be  pumped  directly 
from  the  channel  or  from  neighboring  wells. 

The  hoisting  and  backing  machinery  are  of  three  different 
types,  depending  on  the  method  of  transmitting  the  power:  single, 
double,  and  triple  hitch.  These  three  classes  are  provided  for  by 
the  use  of  a  single,  a  two-part,  or  a  three-part  hoisting  line.  In 
the  first  class,  the  power  developed  by  the  engine  is  compounded 
through  gears,  the  hoisting  rope  being  connected  directly  to  the 
dipper  handle.  In  the  two  latter  classes,  the  power  is  compounded 
by  means  of  a  sheave  attached  to  the  bail  of  the  dipper.  The 
main  engine  is  of  the  double-cylinder,  horizontal,  nonreversible 
type,  mounted  on  a  braced  structural-steel  bed.     There  are  two 


380 


EARTHWORK 


81 


drums,  one  for  the  hoisting  cable  and  the  other  for  the  backing 
cable.  The  drums  are  generally  grooved  to  hold  the  first  layer  of 
cable  in  place  and  are  controlled  by  outside  friction  bands,  which 
are  operated  by  steam-actuated  rams  attached  to  the  spokes  of 
the  large  gearwheel. 

The  swinging  machinery  usually  consists  of  an  independent, 
double-cylinder,  horizontal,  reversible  engine,  which  is  geared  to 
a  shaft  carrying  a  drum  at  each  end  for  direct  leads  to  the  swinging 
circle.     The   engine   is   controlled   by   a   single,   balanced  throttle 


Fig.  47.     Dipper  Dredge  in  Operation 

valve.     On   the    smaller  size    dredges,    the    swinging  mechanism 
consists  of  friction  drums,  gear-driven  from  the  main  engine. 

The  spuds  are  leg  braces  which  are  used  to  provide  stability 
for  the  dredge  during  its  operation.  One  is  located  in  the  center 
of  the  rear  end  and  one  on  each  side  near  the  front  of  the  hull. 
Inclined  bank  spuds  are  used  when  the  channel  is  narrow  and  the 
hull  is  nearly  the  full  width  of  the  excavation.  As  will  be  seen 
from  an  inspection  of  Fig.  47,  the  upper  ends  of  the  spuds  are  attached 
to  the  head  block  of  the  A-frame  and  the  lower  ends  sustain  large 
timber  platforms  which  transmit  the  pressure  directly  to  the  soil. 


381 


82  EARTHWORK 

Short  braces  connect  the  lower  ends  of  the  spud  timbers  with  the 
sides  of  the  hull,  near  the  feet  of  the  A-frame.  Vertical  side  spuds 
are  used  on  the  larger  sizes  of  dredge  for  wide  channel  and  harbor 
work.  In  this  case,  the  lower  ends  of  the  spuds  bear  directly  on 
the  bed  of  the  stream.  The  rear  spud  is  always  vertical  and  is 
used  to  prevent  the  hull  from  swinging  about  during  the  operation 
of  the  excavating  equipment.  Each  spud  is  a  single,  solid  timber 
which  moves  up  and  down  in  an  iron  or  timber  box,  or  guide  frame. 
Teeth  on  a  rack  fastened  to  the  lower  side  of  the  spud,  engage  a 
pinion  on  the  lower  side  and  at  the  end  of  the  guide  frame. 

The  spuds  are  raised  and  lowered  by  means  of  cables  passing 
over  sheaves  and  thence  to  special  drums.  These  drums  are  gen- 
erally mounted  on  a  separate  base,  and  their  shaft  is  connected 
to  the  end  of  the  backing-drum  shaft  by  a  jaw  clutch,  which  is 
disengaged  when  the  spuds  are  not  being  operated.  In  the  larger 
size  dredges  an  independent  engine  is  placed  near  each  spud  and 
operates  the  spud  by  a  direct  gear  connection. 

Excavating  Equipment.  The  excavating  equipment  consists 
of  the  boom,  dipper  handle,  and  dipper. 

The  boom  is  generally  shaped  like  a  fish-beUied  beam  and  may 
be  made  of  either  steel  or  wood.  It  is  made  in  two  sections  so 
spaced  that  the  dipper  handle  may  move  between  them.  For  long 
booms,  a  trussed  type  is  used  to  secure  lightness  with  the  requisite 
strength.  For  long  booms  and  dippers  of  large  capacity,  a  trussed- 
steel  beam  is  preferable.  The  boom  at  its  center  should  have  a 
depth  equal  to  about  ^  o  of  its  length.  The  length  of  the  boom  should 
be  about  1|  times  the  width  of  the  hull  with  vertical  spuds,  and  up 
to  about  twice  the  hull  width  when  bank  spuds  are  used.  The 
upper  end  of  the  boom  is  connected  to  the  yoke  at  the  top  of  the 
A-frame  by  wire  cables.  At  the  outer  end  also  is  the  sheave  over 
which  the  hoisting  cable  passes  on  its  way  from  the  dipper  to  the 
fair-lead  sheaves,  at  the  lower  end  of  the  boom,  and  thence  to  the 
hoisting  drum.  The  lower  end  of  the  boom  is  pivoted  to  the  swing- 
ing circle  or  upper  sections  of  the  base  casting. 

The  swinging  circle  is  a  steel  circular  framework  which  is  located 
just  above  the  deck  or  several  feet  above  the  deck  when  it  is  necessary 
to  secure  sufficient  swinging  power  for  long  booms.  The  diameter 
of  the  circle  should  be  sufficient  to  give  a  direct  pull  from  the  drums 

382 


EARTHWORK  83 

of  the  swinging  engine  and  should  not  be  less  than  j  of  the  hori- 
zontal reach  of  the  boom. 

The  dipper  handle  is  universally  made  up  of  a  solid  timber 
reinforced  with  steel  plates.  Upon  the  lower  side  of  the  handle 
is  placed  the  steel  racking  which  meshes  with  the  pinion  of  the  ship- 
per shaft  located  on  the  upper  side  of  the  boom,  near  its  center. 
The  length  of  the  handle  should  be  made  about  f  that  of  the  boom. 
The  dipper  is  attached  to  the  lower  end  of  the  handle  by  means 
of  a  pin  connection,  so  that  the  pitch  of  the  cutting  edge  may  be 
changed  to  suit  different  classes  of  materials. 

The  dipper  which  is  used  for  the  dredging  of  ordinary  soils 
is  of  the  same  type  as  that  used  on  steam  shovels.  A  reference 
to  Fig.  47  will  show  the  general  shape  and  construction.  The  front 
is  made  of  a  heavy  manganese-steel  plate  which  is  riveted  to  the 
side  plates.  The  back  is  a  single  steel  casting  which  is  also  riveted 
to  the  side  plates.  The  bottom  or  door  is  hinged  to  the  back  and 
is  provided  with  a  latch  which  is  tripped  by  a  rope  extending  to 
the  cranesman's  platform  at  the  right  side  of  the  boom.  The  size 
or  capacity  of  the  dipper  varies  from  |  to  15  cubic  yards;  but  IJ 
yards  is  the  size  generally  used  in  work  of  average  magnitude, 
and  3J  yards  for  large  channels  and  work  of  great  magnitude.  Large 
sea-going  dredges  equipped  with  dippers  of  from  5-  to  10-yard 
capacity  have  been  used  for  several  years  on  harbor  improvements, 
and  in  1914  two  mammoth  dredges,  each  equipped  with  15-yard 
dippers,  were  put  into  operation  on  the  Panama  Canal  for  the 
removal  of  the  slides. 

For  the  excavation  of  loose  sand  and  gravel,  the  clam-shell 
and  orange-peel  buckets  are  very  efficient.  These  are  single-line 
buckets,  and  the  backing  cable  would  not  be  used.  The  details 
and  dimensions  of  a  standard  make  of  clam-shell  and  orange-peel 
buckets  are  given  in  Figs.  48  and  49,  respectively. 

Method  of  Operation.  The  method  of  operation  of  a  dipper 
dredge  is  very  similar  to  that  of  a  steam  shovel,  which  has  been 
previously  described  in  the  section  on  Power  Shovels.  The  crew 
of  a  dipper  dredge  consists  of  an  engineer,  a  cranesman,  a  fireman, 
and  from  2  to  4  laborers,  for  each  shift.  A  dipper  dredge  is  ordi- 
narily run  on  two  11-hour  shifts,  and  hence  two  complete  crews 
are  necessary.    The  engineer  operates  the  levers  and  brakes  which 


383 


84  EARTHWORK 

control  the  motions  of  hoisting,  backing,  swinging,  and  moving  the 
dredge.  The  cranesman  stands  on  a  Httle  platform  just  above 
the  sv/inging  circle  on  the  right  side  of  the  boom,  and  controls  the 
operation  of  the  dipper  as  to  loading  and  dumping.  The  fireman 
supplies  the  boiler  with  fuel  and  has  general  charge  of  the  oiling 
and  care  of  the  machinery.  The  laborers  supply  the  dredge  with 
fuel,  oil,  and  supplies,  and  perform  the  necessary  general  work 
around  the  machine. 

As  the  dipper  and  dipper  handle  slide  downward  toward  the 
face  of  the  excavation,  the  bottom  of  the  dipper  closes  of  its  own 
weight  and  latches.  When  the  dipper  reaches  the  bottom  of  the 
channel,  the  engineer  appHes  the  friction  clutch  to  the  hoisting 
drum  and  throws  a  lever,  starting  the  drum  to  wind  up  the  hoist 
line.  This  pulls  the  dipper  upward,  and  the  forward  motion  is 
regulated  by  the  tension  on  the  backing  line.  As  soon  as  the  dipper 
is  clear  of  the  surface  and  has  completed  the  cut,  the  engineer 
throws  the  hoisting  drum  out  of  gear  and  sets  the  friction  clutch, 
thus  bringing  the  dipper  to  a  stop.  Then  the  swinging  engine  is 
started  and  the  boom  is  swung  around  to  one  side  until  the  dipper 
is  over  the  dumping  place.  With  a  foot  brake,  the  engineer  sets 
the  friction  clutch  and  stops  the  revolution  of  the  swinging  drums. 
The  cranesman  then  pulls  the  latch  rope,  and  this  opens  the  latch, 
releasing  the  bottom  which  drops  and  allows,  the  dipper  contents 
to  slide  out.  The  engineer  then  releases  the  friction  clutch  and 
reverses  the  swinging  engines,  pulling  the  boom  and  dipper  back 
into  position  for  the  next  cut.  As  the  boom  swings  around,  the 
engineer  slowly  releases  the  friction  clutch  of  the  hoisting  and  backing 
drums  and  simultaneously  slightly  pulls  in  the  dipper  toward  the 
dredge  and  lowers  it  into  the  cut,  so  as  to  produce  a  prying  action. 
As  the  latter  part  of  the  drop  is  reached,  the  backing  cable  is  released 
gradually  and  the  dipper  allowed  to  move  forward  toward  the  face 
of  the  cut.  The  time  required  for  a  complete  cycle  of  operations 
depends  upon  the  skill  of  the  operator  and  the  nature  of  the  material 
excavated.  The  average  time  for  a  complete  swing  should  be  about 
40  seconds.  The  most  efficient  results  are  secured  when  the  opera- 
tions are  made  smoothly  and  uniformly  so  as  to  cause  the  least 
amount  of  lost  motion  and  wear  and  tear  on  the  machinery. 

After  the  entire  face  of  the  cut  has  been  removed  within  reach 


384 


EARTHWORK 


35 


of  the  dipper,  the  dipper  is  raised  and  the  boom  slowly  swung  irom 
side  to  side  to  relieve  the  pressure  on  the  spuds.  With  the  boom 
remaining  in  a  central  position,  the  spud  hoists  are  put  in  operation 
and  the  spuds  raised  from  their  resting  places,  thus  allowing  the 
hull  to  float  ahead  toward  the  face  of  the  cut.    With  each  move, 


Fig.  48.     Typical  Clam-Shell  Bucket 
Courtesy  of  The  Hayward  Company,  New  York  City 


CLOsrn 

Open 

Approx. 
Weight 

Capacity 

(lb.) 

Height 

Length 

Width 

Height 

Length 

Ft.       In. 

Ft.       In. 

Ft.       In. 

Ft.       In. 

Ft.       In. 

1|  cu.  yd. 

4400 

7      8 

6       2 

4       2 

8     8 

9       0 

If  cu.  yd. 

4800 

7      8 

6     2 

4     6 

8     8 

9     0 

2    cu.  yd. 

6800 

8     6 

6    11 

4    10 

9     6 

9     9 

2i  cu.  yd. 

7800 

8     9 

7     0 

5      3 

9     9 

10     0 

3    cu.  yd. 

9000 

8     9 

7     0 

6     2 

9     9 

10     0 

the  dredge  makes  an  advance  of  about  6  feet.  The  spuds  are  then 
lowered  by  releasing  the  drums,  or  by  reversing  gears,  and  the  dredge 
is  ready  f«r  the  next  cut. 

Gjst  of  Operation.    The  cost  of  operation  of  a  dipper  dredge 
will  depend  on  the  size  and  type  of  dredge  used,  the  character  and 


385 


86 


EARTHWORK 


magnitude  of  the  work,  the  kind  of  material  to  be  excavated,  the 
efficiency  of  the  operator,  etc. 

Illustratke  Example.    As  a  typical  case,  the  following  is  a 
detailed  statement  of  the  expense  connected  with  the  operation 


Fig.  49.     Typical  Orange-Peel  Bucket 
Courtesy  of  The  Hayward  Company,  New  York  City 


Closed 

Open 

Capacity 

Approx. 

Weight 

(lb.) 

(Cu.  Ft. 
and 

Diameter 

Height 

Diameter 

Height 

Cu.  Yd.) 

Ft. 

In. 

Ft.         In. 

Ft. 

In. 

Ft.          In. 

4     CU.  ft. 

950 

3 

0 

4            8 

3 

9 

5          1 

5     CU.  ft. 

1000 

3 

2 

4         9 

3 

11 

5         3 

7    cu.  ft. 

1100 

3 

6 

5          0 

4 

3 

5         7 

9    cu.  ft. 

1200 

3 

10 

5          2 

4 

7 

5        10 

12    cu.  ft. 

2200 

4 

3 

6          2 

5 

2 

6        10 

15    cu.  ft. 

2350 

4 

7  . 

6          6 

5 

6 

7          2 

21    cu.  ft. 

3800 

5 

1 

7          6 

6 

3 

8         4 

1    cu.  yd. 

4200 

5 

8 

7        10 

6 

10 

8         9 

l\  cu.  yd. 

4600 

6 

0 

8          0 

7 

3 

9          0 

S  1^  cu.  yd. 

5350 

6 

4 

■8          2 

7 

8 

9          4 

\\  cu.  yd. 

7750 

6 

4 

9          4 

7 

10 

10          4 

2    cu.  yd. 

8500 

7 

0 

9        10 

8 

6 

11          0 

2|  cu.  yd. 

9500 

7 

8 

10          2 

9 

3 

11          6 

3    cu.  yd. 

10500 

8 

0 

10          4 

9 

7 

11        10 

S  4    cu.  yd. 

12500 

8 

10 

10        10 

10 

6 

12          6 

386 


EARTHWORK  87 

of  a  dipper  dredge,  equipped  with  a  If -yard  dipper  and  a  70-foot 
boom,  on  the  construction  of  a  drainage  channel  along  the  bottom 
lands  of  a  central  western  river.  The  soil  is  loam  and  clay  with 
no  stone  and  a  small  amount  of  stumps  to  be  removed.  The  channel 
will  be  assumed  to  contain  about  2500  cubic  yards  per  station  of 
100  feet.  Two  crews  work  on  11-hour  shifts  and  live  on  a  houseboat, 
which  floats  along  behind  the  dredge.  The  following  statement  is 
based  on  the  average  output  for  an  11-hour  shift. 

Operating  Cost  of  Dipper  Dredge 

Labor: 

1  engineer,      @  $100  per  month  $4 .  00 

1  fireman,        @    $60  per  month  2 .  40 

1  cranesman,  @>    $75  per  month  3.00 

2  laborers,       @    $50  each  per  month  4.00 

1  cook,  @    $40  per  month  1.60 

Total  labor  cost,  per  day  $15.00 

Fiiel  and  Supplies: 

2  tons  coal,  @  $6 . 00  $12.00 
Oil,  waste,  grease,  etc.            .  2.00 

Total  cost  of  fuel  and  supplies  $14 .  00 

General  and  Overhead  Expenses: 

Board  and  lodging  for  crew  of  10  men,  per  day  $3 .  50 
Repairs  and  incidentals  4 .  00 

Interest  on  investment  (6%  of  $10,000)*  1 .50 

Depreciation  (10%  of  $10,000)*  5.00 

Total  general  expense  $14 .  00 

Total  Cost  of  Operation  for  11-hour  Shift  $43 .  00 

Average  Output  (cu.  yd.)  1200 

Unit  Cost  of  Dipper  Dredging,  per  cu.  yd.,  $43 .  00^  1200  =         00 .036 

Field  of  Usefulness.  The  dipper  dredge  is  the  best  known 
and  most  popular  type  of  excavator  used  in  the  construction  of 
drainage  channels.  Most  of  this  class  of  work  must  be  done  on 
low,  swampy  land,  where  it  is  difficult  for  anything  but  a  boat  to 
move  about.  The  dipper  dredge  with  its  large  bearing  area  and 
shallow  draft  is  especially  adapted  to  operating  under  these  con- 
ditions. Where  the  soil  is  too  soft  to  support  the  smaller  types 
of  dry-land  excavators,  and  a  considerable  number  of  large  stumps 
must  be  removed,  the  smaller  lateral  ditches  of  a  drainage  system 

*  Based  on  200  days  in  a  yega:  and  a  10-year  life. 

387 


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can  be  excavated  more  economically  with  a  small  dipper  dredge 
than  with  any  other  type  of  excavator. 

In  many  cases  it  is  cheaper  to  use  one  of  the  smaller  sizes  of 
dipper  dredge  (having  a  16-foot  width  of  hull,  a  40-foot  boom,  and 
a  1-yard  dipper),  and  to  excavate  a  ditch  twice  the  necessary  size, 
than  to  use  a  smaller  machine  of  another  type  to  dig  a  channel 
the  size  required.  The  most  economical  size  of  channel  for  the 
operation  of  a  dipper  dredge  is  one  with  a  bottom  width  of  40 
feet  and  an  average  depth  of  10  feet.  When  the  cross-section 
of  the  channel  becomes  greater  than  this,  the  cost  increases  until 
a  channel  having  a  cross-sectional  area  of  about  1200  square  feet 
is  reached,  when  the  use  of  the  dipper  dredge  is  no  longer  efficient 
or  practicable. 

The  channel  which  a  dipper  dredge  excavates  is  rather  uneven 
in  cross-section  and  does  not  have  smooth   side  slopes  and  true 


Fig.  50.     Section  of  Ditch  Constructed  by  Floating  Dipper  Dredge 

bottom  grades.  The  form  of  ditch  excavated  by  this  machine 
is  shown  in  Fig.  50.  After  several  years'  use  the  channel  will  assume 
a  general  semicircular  section.  In  shallow  channels,  or  those 
where  the  stream  flow  is  small  during  a  large  part  of  the  year, 
considerable  reduction  of  the  cross-section  may  be  caused  by  the 
deposition  of  silt  and  debris  and  the  growth  of  vegetation. 

The  dipper  dredge  is  one  of  the  most  versatile  of  modern 
excavators  as  it  can  excavate  all  kinds  of  soil  from  silt  to  loose  rock, 
pull  stumps,  remove  boulders,  bridges,  and  other  obstructions, 
drive  piling,  build  earthen  dams,  and  perform  many  other  duties 
which  may  arise  during  the  course  of  operation. 

LADDER  DREDGE 
General   Characteristics.     The  elevator  or  ladder  dredge  has 
been  little  used  in  this  country,  except  in  the  West  and  in  Alaska 
for  placer  mining,  but  which  is  very  popular  and  of  nearly  universal 


388 


EARTHWORK 


89 


use  in  Great  Britain  and  on  the  continent.  Since  1900  the  ladder 
dredge  has  been  used  on  large  waterway  construction;  notably 
the  Chicago  Drainage  Canal,  the  New  York  State  Barge  Canal, 
and  the  Panama  Canal. 

Construction.  The  ladder  dredge  consists  of  a  hull  on  which 
is  placed  the  operating  machinery  and  the  excavating  equipment. 
The  operating  machinery  includes  engines  for  the  operation  of 
the  elevator,  the  belt  conveyors,  the  hydraulic  monitor,  the  spuds, 
etc.  The  excavating  equipment  comprises  the  ladder  frame  and 
ladder,  and  the  means  of  disposal  of  the  excavated  material,  con- 


"Fig.  51.     Elevator  Dredge  Excavating  Large  Drainage  Ditch 

sisting  either  of  a  hopper  and  a  discharge  channel,  or  of  belt  convey- 
ors. The  placer  dredge  is  provided  with  a  revolving  screen  and  dis- 
tributing channels  for  the  separation  of  the  gold  from  the  gravel. 
A  general  view  of  a  ladder  dredge  excavating  a  large  drainage 
channel  is  shown  in  Fig.  51.  A  detailed  view  of  an  electrically 
operated  placer  dredge  is  shown  in  Fig.  52,  and  detailed  views  of 
a  ladder  dredge  especially  designed  for  canal  excavation  are  given 
in  Fig.  53. 

The  hull  or  barge  is  shaped  like  a  rectangular  box  and  is 
generally  built  of  heavy  timbers.  The  hull  may  be  built  as  one 
structure  with  a  well  through  the  bow  for  the  passage  of  the  ladder, 


389 


m 


EARTHWORK 


^^ 

> 

IT  a 

a>  o 

IS 

1^ 


"833 


390 


EARTHWORK 


91 


391 


92  EARTHWORK 

or  as  two  members  with  a  space  between.  The  latter  type  is  some- 
times used  so  that  the  excavator  may  be  passed  in  sections  through 
narrow  structures  such  as  canal  locks. 

The  size  of  the  hull  depends  upon  the  capacity  of  the  dredge. 
The  length,  which  varies  from  50  feet  to  125  feet,  is  generally  about 
five  times  the  width,  which  varies  from  30  feet  to  50  feet.  The  draft 
of  a  ladder  dredge  in  working  condition  is  from  4  feet  to  6  feet  and 
the  depth  of  hull  should  be  from  6  feet  to  10  feet.  The  hull  should 
be  strongly  braced  both  transversely  and  longitudinally  and  made 
watertight  by  well-calked  joints  of  the  outer  planking.  A  few 
hulls  have  been  made  up  of  2  steel-framed  pontoons  connected 
by  steel  cross-frames.  For  permanent  work  this  type  of  hull  is 
better  than  the  wooden  structure,  as  it  is  more  rigid  and  durable. 

Operating  Equipment.  The  power  for  the  operation  of  a 
ladder  dredge  may  be  either  steam  or  electricity. 

Several  independent  engines  are  required  for  the  different 
performances  of  operating  the  ladder,  the  belt  conveyors,  the 
revolving  screen,  the  spuds,  swinging  the  hull,  etc.  These  separate 
engines  are  uneconomical  in  the  use  of  steam  and  hence  it  is  often 
advisable  to  generate  electric  power  by  a  steam  plant  and  operate 
each  engine  by  an  individual  electric  motor.  When  several  dredges 
are  working  in  the  same  locality,  it  is  most  economical  to  locate 
a  power  plant  on  shore  and  to  transmit  the  electric  current  by  wires 
to  the  motors  on  the  machines.  An  economy  in  the  use  of  electric 
power  is  the  saving  of  hull  room  by  the  elimination  of  the  boiler 
and  steam  engines. 

The  operating  equipment  for  a  steam-operated  dredge  con- 
sists of  the  boiler  and  engines  for  the  various  motions.  The  boiler 
is  generally  of  the  Scotch  marine  type  and  is  mounted  on  the  floor 
of  the  hull  in  the  rear  of  the  dredge.  It  should  be  of  more  than  the 
theoretical  estimated  capacity  to  supply  the  engines  and  be  operated 
at  a  working  pressure  of  about  125  pounds. 

The  engines  are  of  the  horizontal,  double-cylinder  type,  which 
have  been  described  in  detail  for  steam  shovels  and  dipper  dredges. 
These  engines  are  gear-connected  to  the  drum  or  winch  machinery. 
The  drums  are  controlled  by  outside  friction  clutches  actuated  by 
small  rams.  Independent  gear  drives  for  the  revolving  screen 
and  ladder  are  often  operated  from  the  main  engine  by  belt  and  pulley 


EARTHWORK 


93 


393 


94  EARTHWORK 

connections.  However,  separate  engines  are  generally  used  for 
the  operation  of  the  spoil  conveyors  and  spuds. 

A  centrifugal  pump,  driven  by  a  separate  engine,  is  generally 
used  to  furnish  water  for  a  hydraulic  monitor,  for  the  hoppers  and 
revolving  screen,  and  for  the  perforated  pipes  which  extend  along 
the  sides  of  the  belt  conveyor  for  cleansing  purposes.  Steam  pumps 
of  standard  type  are  used  to  supply  the  condensers,  feed-water 
heaters,  and  boilers  with  necessary  water. 

When  electric  power  is  used,  individual  motors  are  generally 
mounted  on  the  winch  drum  or  drive  frame  and  gear-connected 
by  a  pinion.  These  motors  may  receive  current  from  a  generator 
operated  by  a  steam  plant  on  the  dredge  or  from  a  steam  or  water 
power  plant  located  on  the  shore. 

Excavating  Equipment.  The  excavating  equipment  consists 
of  the  gantry,  ladder  frame,  and  chain  and  buckets. 

The  gantry  is  an  inclined  framework  composed  of  timber  or 
structural-steel  members  strongly  framed  together.  The  frame 
is  placed  at  the  bow  of  the  hull  and  is  held  in  position  by  braces 
extending  to  the  front  end  of  the  hull.  Sheaves  at  the  top  of  the 
frame  carry  the  cables  which  support  the  outer  and  lower  end  of 
the  ladder  frame.  The  gantry  has  a  height  of  from  15  feet  to  30 
feet.  Fig.  54. 

The  ladder  frame  is  generally  a  structural-steel  framework 
shaped  like  the  boom  of  a  dipper  dredge.  The  length  of  the  frame 
varies  with  the  size  and  capacity  of  the  dredge  and  the  depth  of 
the  proposed  excavation.  The  upper  end  of  the  ladder  frame  is 
hinged  to  the  upper  tumbler  shaft,  while  the  lower  end  is  suspended 
by  heavy  tackle  from  the  gantry.  The  frame  carries  tumblers 
or  large,  hexagonal,  steel  barrels  at  its  ends.  The  upper  tumbler 
is  revolved  by  power  supplied  from  the  main  engine  through  a 
shaft,  while  the  lower  tumbler  is  revolved  by  the  friction  of  the 
bucket  chain. 

The  chain  is  composed  of  a  continuous  series  of  buckets,  links, 
and  connecting  pins.  The  buckets  are  cup-shaped  and  made  of  three 
sections,  strongly  riveted  together.  They  have  capacities  varying 
from  3  cubic  feet  to  13  cubic  feet.  They  are  placed  in  *'open"  or 
"close"  order — that  is,  consecutively,  or  with  open  links  between 
adjacent  buckets — depending  upon  whether  the  soil  is  soft  or  hard. 

394 


EARTHWORK  95 

The  movement  of  the  bucket  chains  is  slow  and  uniform  and 
is  such  as  to  feed  from  15  to  20  buckets  per  minute  into  the  bed  of 
the  stream.  Fig.  55  shows  a  section  of  a  chain  with  ''close"  order 
and  Fig.  54  shows  the  buckets  provided  with  teeth  for  the  excava- 
tion of  dense,  hard  materials. 

One  or  two  spuds  are  generally  placed  at  the  stern  of  the  hull 
to  provide  for  the  stability  of  the  dredge  and  for  its  lateral  movement. 
They  are  usually  composed  of  a  single  timber  with  a  pointed  shoe 
at  the  lower  end  and  are  operated  by  separate  engines  of  the  type 
used  on  the  floating  dipper  dredge. 


Fig.  55.     Section  of  Chain  Used  on  Ladder  Dredge 

Material  Distributing  Machinery.  The  disposition  of  the 
excavated  material  depends  upon  the  character  of  the  work.  In 
placer-mining  operations,  the  dredge  is  provided  with  a  hopper 
into  which  the  material  falls.  Then  the  material  passes  through 
a  revolving  screen  and  upon  a  screen  trough  where  the  gold  is 
collected  by  amalgam  plates.  In  the  excavation  of  canals  or  stream 
beds  the  materials  pass  from  the  hopper  into  a  chute  or  trough 
which  discharges  into  barges,  as  shown  in  Fig.  56,  or  directly 
from  the  bucket  chain  to  belt  conveyors  which  carry  it  to  the  spoil 
banks  along  either  side  of  the  channel,  Fig.  51.  In  some  cases, 
when  the  material  is  to  be  conveyed  for  some  distance,  the  con- 


395 


96 


EARTHWORK 


veyor  is  placed  at  the  stern  of  the  hull  and   discharges  into  a 
series  of  other  conveyors  supported  on  pontoons. 

Method  of  Operation.  The  outer  end  of  the  ladder  is  lowered 
until  the  bucket  chain  is  in  contact  with  the  bed  of  the  stream. 
Each  bucket  in  the  revolution  of  the  chain,  removes  a  slice  of 
material  as  it  comes  into  contact  with  the  soil.  At  the  top  of  the 
ladder,  the  buckets  in  turning  over  the  upper  tumbler,  dump  their 
contents  into  a  hopper  which  discharges  into  a  screen  or  directly 


Fig.  56.     Ladder  Dredge  Provided  with  Trough  for  Discharging  Excavatiou  into  Barges 

upon  a  belt  conveyor.  The  ladder  is  gradually  lowered  as  the 
excavation  proceeds. 

The  dredge  is  swung  from  side  to  side  across  the  channel  by 
wire  cables  attached  to  trees  along  the  shore  and  to  winch  drums 
on  the  hull.  To  move  the  dredge  ahead  the  spuds  are  alternately 
raised  and  lowered  as  the  dredge  is  swung  from  one  side  to  the 
other. 

When  high  banks  are  to  be  removed  it  is  customary  to  use  a 
large  hydraulic  monitor,  which  is  placed  near  the  ladder  frame 


396 


EARTHWORK 


97 


397 


98  EARTHWORK 

i 

and  above  the  deck  of  the  hull  at  the  bow.  Fig.  57  shows  an  ele- 
vator dredge,  equipped  with  a  monitor,  excavating  a  large  irri- 
gation canal  in  the  West. 

The  machinery  of  the  dredge  is  usually  controlled  by  an  operator, 
who  is  located  in  a  small  cabin  placed  near  the  bow  and  above 
the  machinery  house.  Besides  the  operator  there  are  required  an 
engineer,  who  has  general  charge  of  the  machinery,  a  fireman  who 
runs  the  boiler  of  the  steam  equipment,  an  oiler,  a  deck  hand  for 
general  service  on  the  dredge,  a  man  who  has  charge  of  the  opera- 
tion and  control  of  the  conveyors,  and  one  or  more  men  who  have 
charge  of  the  shore  conveyors  or  barges. 

Each  dredge  requires  the  service  of  1  tug  and  from  4  to  8  scows, 
depending  upon  capacity  of  the  dredge,  size  of  channel,  character 
of  materials,  etc.  The  scows  may  be  of  steel  or  timber  and  are 
generally  of  the  bottom-dumping  type  with  several  independent 
compartments. 

Cost  of  Operation.  As  elevator  dredges  are  generally  built 
to  meet  special  conditions  of  service,  it  is  difficult  to  give  any  accurate 
statement  of  the  average  cost  of  operation.  However,  in  order 
to  suggest  the  cost  of  operation  in  canal  excavation,  the  following 
statement  of  the  use  of  ladder  dredges  in  the  construction  of  an 
irrigation  canal  on  a  Reclamation  Service  project  is  given. 

Illustrative  Example,  The  channel  had  a  total  length  of  about 
20  miles  and  in  many  places  the  banks  were  high  on  one  or  both 
sides.  On  fills  and  shallow  cuts,  bulkheads  were  built  along  the 
right  of  way  on  the  lower  bank  to  keep  the  wet  material  from  flowing 
on  to  adjacent  fields.  The  material  excavated  varied  from  a  loose 
gravel  to  hard  pan,  which  in  places  had  to  be  blasted. 

The  dredge  used  was  a  Bucyrus  ladder  dredge,  equipped  with 
steam  power  and  a  3|-cubic-foot  continuous  bucket  chain.  The 
hull  was  built  of  timber,  with  a  length  of  82  feet,  a  width  of  30  feet, 
a  depth  of  6  feet  6  inches,  and  drew  5  feet  of  water.  Steam  was 
furnished  by  2  locomotive-type  boilers,  44  inches  in  diameter  and 
18  feet  long,  and  having  a  rated  capacity  of  80  horsepower.  The 
main  drive  and  ladder  hoist  were  driven  by  an  8  X  12-inch  double 
horizontal  engine  of  70  horsepower.  The  winch  machinery  for 
operating  the  spuds  and  swinging  the  dredge  was  driven  by  a 
2-cylinder,  6  X  6-inch,  double  horizontal  engine  of  20  horsepower. 

398 


EARTHWORK 


99 


The  belt  conveyors  were  operated  by  two  7  X  10-inch,  single-cylinder, 
center-crank,  horizontal  engines  of  18  horsepower.  A  No.  1  Hendy 
hydraulic  giant  was  mounted  on  the  bow  of  the  dredge  and  water 
was  forced  through  it  by  a  2-stage,  6-inch,  centrifugal  pump,  belted 
to  a  10  X  12-inch,  single-cylinder,  upright  engine  of  80  horsepower. 
The  giant  was  used  to  remove  banks  above  the  water  level  and 
beyond  the  reach  of  the  bucket  chain.  Two  belt  conveyors,  one  on 
each  side  of  the  dredge,  were  used  for  the  disposal  of  the  excavated 
material.  Each  conve^^or  was  72  feet  long  and  consisted  of  a  steel 
framework  supporting  a  7-ply,  32-inch,  rubber  conveying  belt. 
Fig.  57  shows  the  dredge  in  operation. 

The  operating  force  consisted  of  8  men  and  4  horses.     Follow- 
ing is  a  schedule  of  the  labor  expense  per  day. 

Expense  Schedule  of  Daily  Labor 


Labor 

Day  Rate 

Superintendent 

$7.50 

Operator 

5.00 

Engineer 

4.67 

Spudman 

3.83 

Fireman 

3.33 

Oiler 

3.00 

Deckman 

2.50 

Man-and-team 

4.50 

The  following  tabulation  gives  the  total  and  unit  cost  of  the 

work. 

Cost  of  Work  by  Ladder  Dredge 

(Excavation  of  929,723  cu.  yd.) 


Cost 

Division 

Total 

Unit 
(per  cu.  yd.) 

Labor  (dredge) 

Labor  (spoil  bank) 

Fuel 

Plant  Maintenance 

Plant  Depreciation 

$29,960.63 
31,159.06 
33,043.07 
52,327.40 
41,432.53 

$0,030 

0.034 
0.036 
0.057 
0.045 

Total 
Engineering  and  Administration 

$187,922.69 
28,154.41 

$0,202 
0.031 

Grand  Total 

$216,077.10 

$0,233 

Field  of  Usefulness.     The  elevator  dredge  has  Been  universally 
used  in  Europe  for  harbor  and  canal  excavation  and  notably  on 


399 


100 


EARTHWORK 


400 


EARTHWORK 


101 


the  construction  of  the  Suez  Canal,  the  Panama  Canal,  and  the 

New  York  State  Barge  Canal.     In  this  country  the  ladder  dredge 

has  not  come  into  general  use  on  account  of  the  high  initial  cost 

of  the  plant.     The   average  American 

contractor  prefers  to  use  a  dipper  dredge 

costing   about   $40,000,  rather  than  a 

ladder  dredge  requiring  an  investment 

of  about  $100,000,  in  order  that  he  may 

secure  immediate  results  on  a  less  capital 

charge. 

The  elevator  dredge  is  efficient  in 
the  excavation  of  all  classes  of  material 
from  silt  to  hard  pan  and  the  softer 
stratified  rocks.  This  dredge  cannot 
work  to  advantage  in  narrow  channels, 
and  hence  is  not  adapted  to  the  excava- 
tion of  small  canals  and  ditches  or  the 
dredging  out  of  narrow  rivers.  In  such 
cases  the  dipper  dredge  should  be  used. 
When  the  banks  are  high,  difficulty  is 
experienced  in  depositing  the  excavated 
material.  When  the  banks  are  low, 
dikes  or  bulkheads  must  be  erected  to 
prevent  the  soft  material  from  flowing 
back  into  the  channel  or  over  adjacent 
land.  When  the  sides  of  the  channel 
are  to  be  sloped,  the  bucket  chain  must 
be  gradually  raised  and  lowered  as  the 
dredge  is  swung  over  to  the  side. 
Trouble  is  often  experienced  in  the 
operation  of  the  spoil  conveyors  and 
water  jets  are  required  to  keep  them 
clean.  The  excavated  material  is  gen- 
erally so  wet  that  the  deposition  of  the 
material  in  uniform  spoil  banks  along 
the  shore  is  a  difficult  matter. 

The  proper  sphere  of  usefulness  of 
the  ladder  dredge  is  in  large  canal,  river, 


401 


102  EARTHWORK 

and  harbor  work,  where  there  are  wide,  long  reaches  and  a  large 
amount  of  dense  material  to  be  removed.  In  such  cases,  the  scow 
method  of  removal  should  generally  be  used. 

HYDRAULIC  DREDGE 

During  the  last  twenty  years,  the  great  improvements  in  the 
rivers,  lakes,  and  harbors  of  this  country  have  made  a  demand  for 
an  excavating  machine  of  great  power,  capacity,  and  efficiency  in 
the  removal  of  large  quantities  of  the  looser  soils.  The  reclamation 
of  the  great  tidal  marshes  along  the  Atlantic  and  Pacific  coasts 
and  the  cleaning  out  of  the  channels  of  the  larger  rivers,  canals,  and 
harbors  are  being  continually  carried  on  by  the  Government.  The 
most  efficient  and  economical  excavator  for  this  class  of  work  is 
the  hydraulic  or  suction  dredge. 

Construction.  The  essential  parts  of  a  hydraulic  dredge  are 
a  revolving  cutter,  a  centrifugal  pump,  and  the  machinery  to  drive 
it,  and  the  barge  or  hull.  Detailed  views  of  a  hydraulic  dredge 
are  shown  in  Figs.  58  and  59. 

The  hull  is  usually  rectangular  in  shape  and  has  a  length  of 
about  3|  times  its  width.  The  size  of  the  hull  depends  on  the 
capacity  of  the  dredge.  The  depth  varies  from  6  feet  to  15  feet, 
providing  a  draft  of  from  3  feet  to  9  feet.  Hulls  are  constructed 
of  wood  or  steel,  but  the  latter  material  is  the  preferable  on  account 
of  its  greater  strength,  durability,  and  rigidity.  Cross-frames 
of  steel  or  wood  are  placed  on  about  2-foot  centers  and  connect 
the  keelsons  and  deck  beams.  This  framework  is  covered  with 
steel  plates  or  heavy  wooden  planking.  The  winch  machinery  is 
placed  on  an  upper  deck  while  the  pumping  machinery  is  placed 
on  a  lower  deck.  A  superstructure  houses  the  machinery  and  con- 
tains the  operating  room  and  usually  living  quarters  for  the  crew. 

At  the  stern  of  the  hull  is  located  a  vertical  frame  from  which 
are  suspended  two  spuds  by  means  of  sheaves  and  cables  leading  to 
the  winch  drums.  The  spuds  are  generally  single  timbers  of  fir, 
pine,  or  oak,  and  are  of  sufficient  length  to  reach  the  bottom  of  the 
excavation  at  high  water. 

Operating  Equipment.  The  operating  equipment  of  a  hydraulic 
dredge  consists  of  the  winch  or  hoisting  engine  and  the  pumping 
equipment. 


402 


EARTHWORK  103 

The  hoisting  engine  controls  the  movement  of  the  barge,  the 
operation  of  the  ladder  and  of  the  spuds.  It  generally  consists 
of  5  drums  which  are  mounted  on  a  single  base  and  operated  by 
a  double-cylinder  engine.  Upon  the  forward  shaft,  the  drums  on 
each  side  swing  the  dredge  and  the  center  drum  is  used  for  the 
raising  and  lowering  of  the  outer  end  of  the  ladder.  The  two  rear 
drums  operate  the  two  spuds  at  the  stern  of  the  barge.  In  some 
cases  a  separate  engine  is  used  to  operate  the  spuds. 

The  pumping  machinery  consists  of  a  centrifugal  pump  and 
the  engine  to  operate  it.  The  pump  is  the  most  important  element 
in  the  construction  and  operation  of  a  hydraulic  dredge.  The 
excavated  material  is  drawn  up  through  the  suction  pipe  and  dis- 
charged through  the  discharge  pipe  to  scows  or  to  spoil  banks  on 
shore.  The  pump  consists  of  a  shell  or  casing  of  circular  form 
with  two  apertures,  one  on  the  periphery  and  the  other  at  the 
center  of  one  side.  Inside  this  shell  revolves  a  set  of  vanes  mounted 
on  a  shaft  which  extends  through  the  center  of  the  casing  and  is 
usually  direct-connected  to  the  engine.  The  vanes  are  generally 
made  in  two  sections;  the  inner  section,  which  is  made  as  a  part 
of  the  shaft;  and  the  outer  sections  which  are  separate  pieces 
bolted  to  the  inner  section.  The  abrasion  by  the  material  passing 
through  the  pump  is  largely  on  the  outer  sections  of  the  vanes, 
which  can  be  easily  unbolted  and  replaced.  The  opening  in  the 
center  of  the  side  is  the  admission  orifice  to  which  the  suction  pipe 
is  attached  and  through  which  the  material  enters  the  casing.  The 
steel  suction  pipe  is  ordinarily  from  15  to  30  inches  in  diameter  and 
varies  in  length  from  10  feet  to  60  feet.  To  the  periphery  of  the 
casing  is  attached  the  discharge  pipe,  which  varies  in  diameter 
from  6  inches  to  48  inches.  A  20-inch  centrifugal  pump  is  shown 
in  Fig.  60. 

The  pump  is  usually  direct-connected  to  a  steam  engine  of 
the  vertical,  marine  type.  For  the  small  sizes  and  capacities, 
compound  engines  are  used,  but  for  large  capacities,  hard  service, 
and  high  heads,  triple-expansion  engines  are  used. 

Excavating  Equipment.  The  excavating  equipment  of  a 
hydraulic  dredge  consists  of  the  gantry,  ladder,  and  cutter.  The 
excavating  equipment  of  a  small  dredge  is  shown  in  Fig.  61. 

The  gantry  is  a  double,  inclined,  timber  frame  which  carries 

403 


104 


EARTHWORK 


the  sheaves  over  which  pass  the  cables  for  raising  and  lowering 
the  outer  end  of  the  ladder. 

The  ladder  is  a  steel-framed  girder  which  is  hinged  to  the  bow 
of  the  hull  at  its  inner  end  and  suspended  by  cables  at  its  outer  end. 
On  the  upper  side  of  the  ladder  is  placed  a  gear-operated  shaft 
which  drives  the  cutter  and  the  suction  pipe. 

The  cutter  is  a  series  of  knives  which  revolve  about  the  hood 
or  circular  mouthpiece  of  the  suction  pipe.  The  type  of  cutter 
used  depends  upon  the  character  of  the  material  to  be  excavated; 
a  heavy,  chrome-steel  head  being  used  for  hard  materials  and  where 


Fig.  60.     Centrifugal  Pump  of  Hydraulic  Dredge 

boulders  are  prevalent,  while  a  light,  open  construction  is  used 
for  soft  materials  and  in  places  where  brush  and  roots  occur. 

Electric  Power  for  Operation.  Dating  from  about  1910,  the 
prevalence  of  cheap  water  power  has  led  to  the  use  of  electric  power 
for  the  operation  of  hydraulic  dredges  in  several  cases.  The  elec- 
trical equipment  includes  the  wound-rotor  type  of  motor  to  operate 
the  cutter,  the  hoisting  engine,  the  pump,  and  the  spuds. 

On  isolated  work,  where  fuel  would  be  expensive  on  account 
of  high  transportation  costs,  but  where  water  power  is  available, 
or  in  the  proximity  of  large  cities  where  electric  power  from  large 


404 


EARTHWORK 


105 


steam  plants  is  obtainable  at  low  rates,  it  will  be  found  more  econom- 
ical to  carry  a  branch  transmission  line  to  the  dredge  and  use  an 
electrical  equipment.  The  advantages  of  compactness,  cleanliness, 
and  efficiency,  which  have  been  previously  discussed  for  the  ladder 
dredge,  are  as  appUcable  in  this  case. 


Fig.  61.     Typical  Hydraulic  Dredge  on  Canal  Con.structioa 
Courtesy  of  Great  Lakes  Dredge  end  Dock  Company,  Chicago 

Method  of  Operation.  The  dredge  is  held  in  position  by  cables 
which  extend  from  the  main  or  hoisting  engine  to  anchorages  on 
either  side  of  the  bow,  and  by  the  two  spuds  in  the  stern  of  the  hull. 
By  alternately  raising  a  spud  and  winding  up  and  unwinding  the 
cables,  the  dredge  may  be  swung  from  side  to  side  so  as  to  cover 
a  wide  area. 

The  revolving  cutter  excavates  the  material,  which  may  vary 


405 


106  EARTHWORK 

from  silt  to  hard  pan.  The  disintegrated  material,  diluted  by  water, 
is  sucked  up  through  the  suction  pipe  into  the  pump  and  then  forced 
out  through  the  discharge  pipe  which  is  carried  by  pontoons,  and 
discharges  into  scows  or  out  upon  an  area  which  is  to  be  filled  in. 

Cost  of  Operation.  It  is  impossible  to  give  any  accurate 
statement  as  to  the  average  cost  of  excavation  with  a  hydraulic 
dredge.  Such  a  dredge  on  work  of  any  magnitude  is  usually  made 
especially  for  the  particular  conditions  at  hand  and  the  cost  of 
operation  may  vary  within  rather  wide  limits. 

Illustrative  Example.  Following  is  a  t^^pical  labor  schedule 
for  the  operation  during  an  8-hour  shift  of  a  hydrauhc  dredge 
equipped  with  a  20-inch  centrifugal  pump. 

Labor  Expense  Schedule 


Labor 

M( 

JNTHLY  Rate 

1  operator 

$100.00 

1  engineer 

100.00 

1  engineer 

80.00 

3  firemen,  @  $70.00  each 

210.00 

1  spudman 

60.00 

1  oiler 

50.00 

4  deck  hands, 

@  $50.00  each 

200.00 

The  average  cost  of  operation  would  depend  upon  the  size 
and  capacity  of  the  dredge,  the  character  of  the  material,  efficiency 
of  operation,  kind  of  power  used,  etc.  Records  of  recent  work  show 
a  range  of  from  4  cents  to  15  cents  per  cubic  yard  for  materials 
varying  from  sand  to  indurated  gravel. 

Field  of  Usefulness.  Hydraulic  dredges  have  been  in  use 
for  the  last  half  century,  but  their  greatest  development  has  been 
during  the  last  two  decades,  since  1895.  In  Europe  their  use  has 
been  largely  in  the  maintenance  of  channels  in  the  large  rivers 
and  in  the  construction  of  great  canals.  In  this  country  they  have 
been  used  principally  in  the  reclamation  of  low,  wet  lands,  along 
rivers,  lakes,  and  harbors,  the  construction  of  great  artificial  water- 
ways, such  as  the  New  York  State  Barge  Canal  and  the  Panama 
Canal,  and  the  maintenance  of  channels  in  large  inland  waterways, 
such  as  the  Mississippi  River. 

The  earlier  types  of  hydraulic  dredge  were  provided  with  an 
agitator  and  water  jets  at  the  mouthpiece  end  of  the  suction  pipe, 
and  hence  they  could  handle  only  the  softer  soils,  such  as  silt,  sand, 

406 


EARTHWORK 


107 


f  1 

r 
I 


407 


108 


EARTHWORK 


and  clay.      In  recent   years,  however,  the  cutter  head  has  been 
developed  in  different  forms,  and  very  hard  dense  soils  can  be 

loosened  and  broken  up  sufficiently  to 
be  discharged  through  the  pump.  ! 
The  hydraulic  dredge  is  not  an' 
economical  type  of  machine  to  use  in 
the  construction  of  levees  or  in  canal 
excavation  where  the  disposition  of 
the  excavated  material  must  be  madd 
within  a  confined  space.  The  material 
as  it  emerges  from  the  discharge  pipe 
is  [in  such  a  [high  state  of  dilution 
that  it  will  not  remain  in  place  unless 
confined  within  banks  or  bulkheads. 
Some  method  of  removing  the  sur- 
plus water  in  the  discharge  pipe  may 
be  used  effectively;  one  such  method 
being  the  installation  of  overflow 
strainers  placed  at  intervals  in  the 
upper  sections  of  the  pipe. 

This  type  of  dredge  is  unique 
among  excavators  in  its  abihty  to 
discharge  the  excavated  material  in 
any  direction  and  at  a  considerable 
distance  from  the  site  of  the  excava- 
tion. This  wide  range  of  disposal  is 
of  especial  value  in  the  filling  in  of 
waste  lands  along  waterways. 

SUBAQUEOUS  ROCK  BREAKERS 
LOBNITZ  ROCK  CUTTER 

For  use  in  connection  with  the 
beds  of  channels  through  very  indu- 
rated materials  or  rock  which  must 
be  broken  up  before  the  removal  by 
dredge,  there  are  two  radically  differ- 
ent types  of  rock  breakers :  the  Lob- 
nitz  rock  cutter;  and  the  drill  boat. 


t- 


Ql__. 


408 


EARTHWORK  109 

The  Lobnitz  rock  cutter  consists  of  a  heavy  chisel  of  steel, 
weighing  from  4  tons  to  15  tons,  and  equipped  with  a  hardened- 
steel  cutting  point.  The  chisel  is  raised  to  a  height  of  from  5  to 
10  feet  and  then  dropped  upon  the  surface  of  the  hard  material. 
The  impact  of  the  falling  point  serves  to  splinter  and  fracture  the 
material  so  that  it  can  be  removed  by  the  dipper  of  a  floating  dipper 
dredge,  or  by  the  buckets  of  a  ladder  dredge.  The  cutter  is  capable 
of  breaking  up  the  hardest  rock,  in  layers  3  feet  thick  at  a  time. 
The  cutter  is  mounted  on  a  hull  composed  of  two  barges,  rigidly 
connected  by  cress-frames.  The  details  of  a  Lobnitz  rock  cutter 
are  shown  in  Figs.  62  and  63. 

In  Europe,  where  this  form  of  rock  breaker  is  in  general  use, 
the  ladder  dredges  are  often  provided  with  several  picks  or  chisels, 
located  in  a  well  alongside  of  the  ladder.  These  chisels  are  placed 
about  2  feet  apart  and  are  operated  singly  or  in  unison.  The  picks 
are  generally  made  of  heavy  timbers  which  are  provided  with  hard- 
ened-steel points.  The  buckets  of  the  ladder  dredge  are  made 
especially  heavy  and  provided  with  teeth  on  the  cutting  edges. 
With  a  10-pick  ladder  dredge,  an  excavation  of  43  tons  of  hard 
rock  per  hour  has  been  made. 

\ 
THE  DRILL  BOAT 

Speed  a  Characteristic.  The  Lobnitz  rock  cutter  has  not  found 
favor  in  this  country  on  account  of  its  slow  speed  and  cumbersome 
method  of  operation.  Hence,  a  drill  boat  has  been  devised  and 
this  machine  uses  the  standard  steam-actuated  percussion  drills, 
which  provide  great  lifting  and  striking  power  combined  with  a 
larger  number  of  blows  per  minute. 

The  drill  boat  consists  ^f  a  barge  equipped  with  a  spud  at 
each  corner  to  support  it  upon  the  bed  of  the  stream  during  the 
drilling.  Each  of  the  four  spuds  is  operated  by  a  pair  of  independent 
engines  geared  to  a  rack  on  the  side  of  the  timber.  When  the  drills 
are  in  operation,  the  spuds  are  forced  down  until  the  boat  is  raised 
above  the  height  of  normal  flotation.  The  constant  elevation  of 
the  boat  is  maintained  by  the  automatic  regulation  of  the  steam 
pressure  in  the  spud  engines. 

The  drills  are  steam-operated  percussion  drills,  similar  in 
design  and  operation  to  the  ordinary  steam  drills  used  in  drilling 

409 


no 


EARTHWORK 


410 


EARTHWORK        '  111 

on  land.  The  piston  diameter  is  from  5 J  inches  to  0§  inches,  and 
the  drills  are  mounted  on  movable  steel  towers,  which  run  on  a 
track  along  the  side  of  the  barge.  The  drills  may  be  raised  or 
lowered  along  vertical  guides  15  feet  to  30  feet  in  length.  The 
feed  of  the  drill  is  controlled  by  hydraulic  plungers  having  a  stroke 
equaling  the  length  of  the  guides  and  moved  by  long  screws  which 
arc  operated  by  small  engines.  The  towers  are  moved  along  the 
track  by  steam  or  by  hydraulic  power. 

A  view  of  the  drill  side  of  a  drill  boat  drilling  and 
blasting  bed  rock  in  Boston  Harbor  channel,  is  shown  in 
Fig.  64. 

Cost  of  Operation.  The  output  and  cost  of  operation  of  a 
drill  boat  depends  upon  the  number  and  size  of  drills,  the  character 
of  the  rock,  the  depth  of  excavation,  etc.  It  is  impossible  to  state 
any  general  rules  which  may  be  used  in  this  class  of  work.  The 
following  statement  is  given  as  a  typical  case  of  the  use  of  a  drill 
boat  in  channel  excavation. 

Illustrative  Example.  The  work  consisted  in  the  excavation 
of  a  ship  channel,  200  feet  wide  and  17  feet  deep,  in  a  large  river. 
The  material  was  a  very  hard  limestone  rock  occurring  in  strata 
from  20  inches  to  30  inches  thick.  The  work  was  carried  on  in  a 
stream  having  a  current  of  from  8  miles  to  12  miles  an  hour,  in  an 
area  of  turbulent  water. 

The  drill  boat  was  equipped  with  four  5-inch  drills,  which 
operated  through  four  slots,  each  20  feet  long  and  18  inches  wide, 
and  located  in  the  forward  part  of  the  barge.  The  drill  frames 
carried  steel  drill  spuds  with  pipe  guides  for  the  drill  bars,  and  were 
arranged  to  move  along  tracks  the  length  of  the  wells.  Thus  each 
drill  made  several  holes  at  each  set-up  of  the  barge.  Holes  were 
drilled  and  blasted  in  groups  of  four.  The  rock  was  drilled  below 
grade  to  a  depth  equal  to  half  the  hole  spacing,  which  was  about 
6  feet.  The  dynamite  used  was  proportioned  on  a  basis  of  about 
1  pound  to  a  cubic  yard  of  rock. 

The  barge  was  supported  on  four  20  X  20-inch  power-controlled 
spuds.  Gear  drums  operated  five  IJ-inch  breasting  chains,  one 
leading  upstream,  and  two  over  each  side.  Each  chain  was  attached 
to  an  anchor  weighing  about  1  ton. 

The  monthly  cost  of  operation  is  as  follows: 

411 


112 


EARTHWORK 


Labor: 


Operating  Cost  of  Drill  Boat 


1  captain  $100.00 

4  drillers,  @  $75 .  00  each  300 .  00 

4  helpers,  @  $30 .  00  each  1 20 .  00 

1  fireman  30.00 

1  machinist  65.00 

1  blacksmith  70.00 

1  helper  30.00 

1  blaster  60.00 

1  helper  35.00 

1  cook  30.00 

Total  labor  expense,  per  month 
Board  and  Lodging: 

16  men,  @  $12.00  each,  per  month 
Fuel  and  Supplies: 


$840.00 


$192.00 


60  tons  coal,  @  $4 .  00                         $240 .  00 

Oil,  and  waste 

40 

.00 

Blacksmith's  coal 

15, 

.00 

Steel,  iron,  and  suppUes 

52.00 

$347.00 

Total  fuel  and  supplies 

Grand  total,  per  month 

$1,379.00 

Cost  of  Drilling,  per  drill  hour 

1.105 

Cost  of  Drilling,  per  foot  drilled 

0.049 

Average  Depth  of  Drilling,  per  hour  (ft.) 

21 

Depth  of  Drilling  (ft.) 

0  to  11 

Field  of  Usefulness.  The  two  types  of  rock  breakers  are 
very  efficient  for  subaqueous  rock  drilling  and  give  results  which 
compare  favorably  with  drilling  on  land. 

The  Lobnitz  rock  cutter  works  most  efficiently  in  shallow 
cuttings  of  stratified  rock,  which  is  easily  shattered.  The  drill 
boat,  of  the  American  type,  does  its  most  efficient  work  in  hard 
rock  of  depths  of  over  3  feet. 

TRENCH  EXCAVATORS 

•  Classification.  The  great  amount  of  trenching  necessitated 
by  the  construction  of  sewer,  water-supply,  and  drainage  systems 
has  led,  in  recent  years,  to  the  development  and  use  of  excavators 
especially  adapted  to  this  class  of  work.  These  trench  machines 
are  more  efficient  and  economical  than  hand  labor  on  work  of  any 
magnitude. 


412 


EARTHWORK 


113 


Trench  excavators  may  be  divided  into  two  general  classes 
as  follows: 

(1)  Sewer  and  water-pipe  trench  excavators. 

(2)  Drainage-tile  trench  excavators. 


Fig.  65.     Traveling  Derrick  on  Trench  Excavation  Work 
Courtesy  of  Brown  Hoisting  Machinery  Company,  Cleveland,  Ohio 


413 


114  EARTHWORK 

PIPE=TRENCH  TYPES 

This  class  of  excavators  embraces  five  distinct  types  as  follows : 
the  traveling  derrick  or  locomotive  crane,  the  continuous  bucket 
excavator,  the  trestle-cable  excavator,  the  trestle-track  excavator, 
and  the  tower  cable  way. 

TRAVELING  DERRICK 

The  traveling  derrick  or  locomotive  crane  is  a  very  useful 
and  adaptable  type  of  excavating,  hoisting,  and  conveying  machine. 
It  has  been  serviceable  in  many  lines  of  construction  work  as  the 
machine  may  be  used  for  excavation,  transportation  of  various 
kinds  of  materials,  loading  and  unloading  wagons,  cars,  barges, 
etc.  In  this  discussion,  we  will  consider  the  machine  only  as  a 
trench  excavator. 

Construction.  The  essential  parts  of  a  traveling  derrick  are 
the  car,  the  hoisting  engine,  and  the  derrick.  The  machines  are 
made  in  capacities  varying  from  3  tons  to  20  tons.  A  machine  on 
trench  excavation  is  shown  in  Fig.  65. 

The  car  is  a  steel-frame  platform  which  supports  directly 
the  cast-iron  turntable  bed  and  the  counterweights.  The  platform 
is  mounted  on  a  4-wheel  truck,  equipped  either  with  broad-tired 
w^heels  for  road  traction,  or  with  standard  railroad  wheels  for  the 
smaller  sizes  of  crane.  The  larger  sizes,  generally  above  10-ton 
capacity,  are  mounted  on  two  4-wheel  trucks,  equipped  w^ith  stand- 
ard railroad  wheels.  The  car  is  provided  with  drawbars  for  the 
4-wheel  type,  and  couplers,  steam  brake,  grab  handles,  steps,  etc., 
for  the  8- wheel  type. 

Operating  Equipment.  The  power  for  the  cranes  may  be 
steam,  electric,  or  that  furnished  by  an  internal-combustion  engine. 
Ordinarily  steam  power  is  used,  but  the  other  kinds  would  be 
more  economical  when  the  cost  of  coal  or  wood  is  high  compared 
with  electric  power  and  gasoline. 

The  steam  equipment  consists  of  a  boiler,  engine,  hoisting 
mechanism,  rotating  mechanism,  and  traveling  mechanism.  The 
boiler  is  of  the  vertical,  tubular  type,  and  should  be  capable  of  work- 
ing at  a  pressure  of  100  pounds  with  quick-steaming  qualities  and 
large  steam  capacity.  The  engine  is  usually  of  the  vertical,  double- 
cylinder   type,   provided   with   link-motion  reversing  gear,   wide- 

414 


EARTHWORK 


115 


g  ;5 


H| 


415 


116  EARTHWORK 

ported  slide  valves,  etc.  The  hoisting  mechanism  consists  of  a 
double-drum  winch.  The  hoist  drum  is  driven  from  a  friction 
clutch  on  the  main  engine  shaft.  The  shell  drum  is  operated  from 
the  hoist  drum  by  a  slip  friction.  Both  drums  are  controlled  by 
friction-clutch  brakes,  lever-operated  by  one  man.  The  rotating 
mechanism  consists  of  2  friction  clutches  driving  a  chain  of  gears. 
The  upper  platform,  which  supports  the  operating  and  excavating 
equipments,  can  be  revolved  in  either  direction  through  a  complete 
circle.  The  traveling  mechanism  consists  of  a  set  of  gears  driven 
by  a  friction  clutch  on  a  shaft  geared  to  the  crank  shaft  of  the  engine. 
The  machine  may  be  moved  in  either  direction. 

Excavating  Equipment.  The  excavating  equipment  consists 
of  the  boom  or  crane,  and  the  dipper  or  bucket.  The  boom  is  a 
steel-frame  structure,  hinged  at  its  lower  end  to  the  front  of  the 
upper  platform,  and  supported  at  its  outer  and  upper  end  by  guys 
extending  to  the  rear  corners  of  the  platform.  At  the  outer  end 
of  the  crane  is  the  sheave  over  which  the  hoist  line  passes  on  its 
path  from  the  drum  to  the  bucket. 

The  bucket  or  dipper  may  be  a  grab  bucket,  of  the  orange- 
peel  or  clam-shell  type,  or  a  drag-line  dipper.  The  former  is  used 
for  the  excavation  of  softer  soils  while  the  latter  is  more  serviceable 
in  the  removal  of  the  denser  and  harder  soils.  In  the  latter  case, 
a  separate  drag-line  drum  must  be  provided  in  the  hoisting 
mechanism.  A  traveling  derrick  using  a  drag-line  bucket  in  canal 
construction  is  shown  in  Fig.  66. 

Method  of  Operation.  A  traveling  derrick  is  operated  by 
a  crew  of  three  to  ten  men,  depending  on  the  amount  of  extra  labor 
necessary.  An  engineer  controls  all  the  operations  of  excavating, 
rotating,  and  traveling,  a  fireman  operates  the  boiler,  a  signalman 
is  often  necessary  for  deep-trench  work,  and  one  or  more  laborers 
are  used  for  general  service  about  the  machine  and  in  the  excava- 
tion.    When  a  skip  is  used,  shovelers  are  required. 

The  method  of  operation  is  very  vsimilar  to  that  of  a  revolving 
shovel  and  the  student  is  referred  to  that  section  of  the  text  for 
a  complete  discussion  of  this  subject. 

On  trench  excavation,  one  machine  may  be  used  for  excavation 
only,  or  may  excavate  and  later  return  to  back  fill.  On  large 
works,  it  has  been  found  advantageous  to  use  two  or  more  machines 

416 


EARTHWORK  117 

coordinately;  one  for  the  rough  excavation,  one  for  the  finished 
excavation  and  for  handUng  pipe  and  materials,  and  one  for  the 
back  fining. 

Cost  of  Operation.  The  cost  of  operation  would  vary  greath* 
with  the  size  of  the  machine,  the  efficiency  of  its  operation,  the 
character  of  the  material,  etc.  Thejollowing  statement  is  given  as 
an  approximate  idea  of  the  cost  of  operation  under  average  con- 
ditions. 

Illustrative  Example.  A  10-ton  machine,  equipped  with  an 
automatic  clam-sheU  bucket  of  1-yard  capacity,  and  moving  on  a 
track  along  the  side  of  the  trench,  will  be  considered.  The  material 
is  clay  for  a  depth  of  8  feet,  and  is  underlaid  by  a  substratum  of 
gravel.  Following  is  an  estimate  of  the  cost  of  operation  for  a 
10-hour  working  day: 

Operating  Cost  of  Traveling  Derrick 

Labor: 


1  engineer 
1  fireman 
3  laborers,  @  $2 .  00  each 

Total  labor  cost,  per  daj' 
Fuel  and  Supplies: 

1  ton  coal 

Oil,  waste,  and  repairs 

$5.00 
2.50 
6.00 

$4.00 
1.50 

$13.5© 

Total  fuel  and  supplies 
General  and  Overhead  Expenses: 

Depreciation  (5%  of  $5000)* 
Interest  (6%  of  $5000)* 
Incidental  expenses 

$1.25 
1.50 
2.25 

$5.50 

Total  general  expense 

$5.00 

Total  Cost  of  Work  for  10-hour  Day  $24 .  00 
Total  Excavation  for  10-hour  Day  (cu.  yd.)                       400 
Unit  Cost  of  Traveling  Derrick  Excavation,  per  cu.  yd., 

$24.00^400=  00.06 

Field  of  Usefulness.  The  traveling  derrick  is  economical  for 
trench  excavation  when  the  soil  is  loam,  clay,  sand,  or  gravel,  and 
can  be  easily  handled  by  a  grab  bucket,  or  a  drag  or  scoop  bucket. 
This  type  is  especially  adapted  for  wide  trenches,  over  5  feet  in 
width,  which  cannot  be  readily  excavated  by  other  t>T>es. 

*  Based  upon  200  working  days  in  a  year  and  a  20-year  life. 

417 


118 


EARTHWORK 


This  type  of  excavator  is  very  efficient  with  good  management, 
as  it  may  be  used  for  excavation,  back  fiUing,  and  pulhng  sheeting. 

CONTINUOUS  BUCKET  EXCAVATOR 
Construction.    There  are  several  makes  of  machine,  which  are 

especially  devised  for  the  digging  of  trenches  with  vertical  sides. 

This  type  of  excavator  has  been  developed  in  recent  years  to  meet 

the  demand  for  a  machine   for  municipal  work   under  favorable 

conditions  of  soil  and  for  large  work. 

An  analysis  of  continuous  bucket  excavators  shows  the  following 

essential  parts:  a  frame  supported  on  wheel  trucks,  the  operating 


67.     Diagram  of  Parsons  Trench  Excavator 
Courtesy  of  G.  W.  Parsons  Company 


mechanism,  and  the  excavating  mechanism. 
All  makes  are  built  on  the  principle  of  the 
continuous  excavator  or  ladder  dredge,  and 
differ  only  in  details  of  construction. 

The  platform  is  built  of  steel  members 
strongly  braced  and  framed  together.  It  may 
be  supported  on  2  trucks  equipped  with 
broad-tired  wheels,  or  made  in  two  sections  and  supported  on  3 
trucks.  In  the  latter  case,  the  rear  section  which  carries  the  exca- 
vating chain  is  hinged  to  the  main  section  and  is  supported  on  1 
truck.  Fig.  67  shows  a  diagrammatic  view  of  this  type,  and  Fig.  68 
shows  a  view  of  the  single-platform  machine. 

Operating  Equipment.    A  steam  or  internal-combustion  engine 
may  be  used.    The  latter  is  more  economical  in  sections  of  the 


418 


EARTHWORK  119 

West  where  coal  is  expensive,  and  is  cleaner,  more  compact,  and  does 
away  with  the  use  of  a  fireman  and  the  discomfort  of  a  boiler  in 
warm  weather. 

A  steam-power  equipment  consists  of  a  boiler,  an  engine,  and 
the  transmission  mechanism.  The  boiler  is  of  the  vertical,  tubular 
type  and  is  placed  near  the  front  end  of  the  platform.  The 
engine  is  placed  behind  the  boiler  and  is  of  the  single-cylinder, 
vertical  type.  Power  is  transmitted  to  the  bucket  chain,  the  dis- 
posal conveyor,  and  the  central  axle,  for  traction  through  gears 
and  sprocket  chains. 


Fig.  68.     Chicago  Trench  Excavator 
Courtesy  of  F.  C.  Austin  Drainage  Excavator  Company,  Chicago 

Excavating  Equipment.  The  excavating  equipment  consists 
of  the  bucket  chain,  and  the  disposal  conveyor.  The  bucket  chain 
in  one  type  of  machine  comprises  an  endless  chain  moving  over 
sprocket  wheels  on  the  ends  of  an  arm,  which  is  suspended  from 
the  rear  end  of  the  platform  and  is  adjusted  to  permit  of  the  exca- 
vation to  the  proper  grade  regardless  of  inequalities  of  the  surface 
over  which  the  machine  passes.  In  the  other  type  of  trench 
machine,  a  circular  wheel  is  suspended  from  the  rear  of  the  platform 
and  revolves  on  a  central  axle. 

The  buckets  are  attached  to  the  sprocket  chain  or  to  the 
periphery  of  the  wheel.  They  are  scoop-shaped  and  provided  with 
cutting  edges  or  teeth,  depending  upon  the  nature  of  the  material 
to  be  excavated.    The   width  of   the  trench  is  governed  by  the 

419 


120 


EARTHWORK 


width  of  the  buckets,  which  are  made  in  several  widths  and  can 
be  easily  removed  and  changed.  In  one  make  of  machine,  an 
increased  wddth  of  trench  can  be  secured  by  moving  the  whole  bucket 
chain  sideways  along  the  supporting  frame.  This  arrangement 
provides  for  the  excavation  of  a  trench  up  to  6  feet  in  width  without 
changing  the  buckets  and  also  the  excavation  of  a  manhole  at  any 
point  without  delay.  Fig.  69  shows  a  sectional  bucket  used  on 
the  Parsons  Trench  Excavator. 


Fig.  69.     Sectional  Buckets  Used  on  Parsons  Trench  Excavator 

The  disposal  conveyor  consists  of  a  belt  conveyor  placed  at 
the  rear  of  and  transversely  to  the  platform.  Its  elevation  is  below 
the  top  of  the  bucket  chain.  At  the  top  sprocket,  the  buckets 
turn  over  and  deposit  the  material  on  this  moving  belt,  which 
conveys  it  to  one  side  of  the  trench  and  deposits  it  in  a  spoil' 
bank. 

Method  of  Operation.  The  labor  crew  necessary  to  operate 
a  trench  excavator  depends  on  the  character  and  magnitude  of 
the  work  and  the  kind  of  power  used.  With  a  steam-power  equip- 
ment, an  engineer  or  operator,  a  fireman,  and  one  or  more  helpers 


420 


EARTHWORK 


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421 


122  EARTHWORK 

will  be  required.  The  operator  has  direct  charge  of  the  operations 
of  excavation  and  traction.  The  fireman  operates  the  boiler  and 
has  general  supervision  of  the  engine.  The  helpers  are  of  general 
service  in  furnishing  the  machine  with  fuel,  w\ater,  and  supplies, 
in  bracing  the  trench  when  necessary,  and  in  general  service  about 
the  work. 

The  bucket  chain  moves  downward  and  inward  and  removes 
a  thin  slice  of  material  as  each  bucket  comes  in  contact  with 
the  soil.  The  .depth  of  cut  is  regulated  by  raising  and  lowering 
the  free  end  of  the  frame.  When  obstructions,  such  as  cross  pipes, 
large  boulders,  etc.,  occur,  the  chain  may  be  raised  over  them  and 
fed  down  into  the  earth  on  the  other  side.  The  material,  from  the 
top  of  the  revolving  chain  or  wheel,  falls  upon  the  belt  conveyor 
and  is  carried  to  either  side  of  the  trench,  making  a  continuous 
spoil  bank. 

When  one  section  has  been  excavated,  the  machine  moves 
ahead  and  starts  another  slice.  The  excavating  chain  or  wheel 
can  be  raised  clear  of  the  surface  and  the  machine  moved  over  ordi- 
nary roads  at  a  speed  of  about  1  mile  per  hour.  Table  VI  gives  the 
dimens'ions,  weights,  capacities,  and  costs  of  three  different  makes 
of  trench  excavator. 

Cost  of  Operation.  The  following  comparison  of  the  cost  of 
excavation  of  a  trench  by  hand  and  by  machine  labor  will  be  of 
interest  to  the  student,  who  is  urged  to  make  a  close  study  of  the 
method  of  analysis. 

Illustrative  Example.  The  soil  is  clay  and  loam  and  the  ground 
surface  fairly  level  and  solid  enough  to  support  a  trench  machine. 
The  trench  has  a  width  of  28  inches  and  an  average  depth  of  12 
feet.  Each  laborer  will  excavate  7  cubic  yards  per  10-hour  day 
and  as  the  material  must  be  rehandled  for  the  last  3  feet  of  depth 
of  cut,  we  will  assume  5  extra  men  for  the  work  and  not  include 
their  output.  A  crew  of  45  men  will  dig  350  feet  of  trench  during 
a  10-hour  day  and  the  total  excavation  will  be  about  315  cubic  yards. 
The  same  crew  will  back  fill  at  a  cost  of  7  cents  per  cubic  yard. 
The  machine  will  excavate  250  feet  of  trench  per  10-hour  day. 
The  back  fiUing  will  be  done  by  teams  and  scrapers. 

Following  is  a  detailed  statement  of  the  cost  of  the  work  for 
the  two  methods,  based  on  a  10-hour  day. 

422 


EARTHWORK 


123 


Cost  of  Trench  Excavation  by  Hand 

Labor: 

1  foreman 

1  timberman  , 

1  helper 
1  pipe  layer 
1  helper 
50  laborers,  @  $2 .  00  each 

Total  labor  cost  for  excavation 
Back  filling  315  cubic  yards,  @  7c 

Total  cost  of  Hand  Work  for  a  10-hour  Day 


%   4.00 

3.00 

2.50 

3.00 

2.50 

100.00 

$115.00 

22.00 

$137.00 


Cost  of  Trench  Excavation  by  Machine 

Labor: 

1  foreman  $  4.00 

1  timberman  3.00 

1  helper  2.50 

1  pipe  layer  •                            3 .  00 

1  helper  2.50 

1  engineer  4.00 

1  fireman  2 .  50 


3  teams,  (c 
2  laborers, 


$4.00each| 


hauling  for  excavator 
2  back  filling  trench 
$2.00  each 


12.00 
4.00 


Total  labor  cost,  per  day 
Fuel  and  Supplies: 
1  ton  coal 
Oil,  and  waste 
Water 

Total  fuel  and  supplies 
Overhead  and  General  Expenses: 
Interest  (6%  of  $6000)* 
Depreciation  (10%  of  $6000)* 
Repairs 
Incidentals 

Total  general  and  overhead  expenses 
Total  Cost  of  Operation  for  a  10-hour  Day 


$5.00 

1.00 

1.00 

$1.80 

3.00 

2.70 

4.50 

$37.50 


$7.00 


$12.00 


$56.50 


Total  cost  of  excavation  of  315  feet  of  trench,  pipe  laying,  and 
back  filling  by  hand  work,  for  a  10-hour  day,  is  $137.00. 

Total  cost  of  excavation  by  machine  of  225  feet  of  trench, 
pipe  laying  by  hand  work,  and  back  filling  by  scrapers  is  $56.50. 

*Based  upon  200  working  days  in  a  year  and  a  10-year  life. 


423 


124  EARTHWORK 

A  comparison  of  the  above  results  shows  that  during  a  10-hour 
day,  a  trench  excavator  will  do  about  70  per  cent  of  the  amount  of 
trench  excavation  that  can  be  done  by  hand  labor  and  at  40  per 
cent  of  the  cost. 

Field  of  Usefulness.  The  continuous  bucket  excavator  is 
especially  adapted  for  trench  excavation,  where  the  width  does 
not  exceed  72  inches  and  the  depth  20  feet,  and  the  soil  conditions 
are  favorable.  This  is  especially  true  through  the  IVIiddle  West, 
where  clay  and  loam  with  few  obstructions  such  as  boulders,  roots, 
etc.,  predominate  up  to  shallow  depths. 

On  account  of  the  great  weight  of  the  machines,  they  are  not 
practicable  for  use  in  soft,  wet  soils,  unless  mounted  on  caterpillar 
tractors.  For  the  excavation  of  hard  soils,  considerable  trouble 
is  often  experienced  on  account  of  the  breaking  of  the  bucket  chain. 
Hence  it  is  desirable  to  use  a  machine  with  a  strong,  heavy  chain 
for  the  digging  of  hardpan,  blue  clay,  and  other  hard,  tough  materials. 

The  trench  excavator  is  efficient  and  economical  for  the  exca- 
vation of  trenches  24  inches  and  over  in  width  and  over  6  feet  in 
depth,  and  one  machine  can  do  the  work  of  from  80  to  200  men. 

TRESTLE  CABLE  EXCAVATOR 

Construction.  The  trestle  cable  excavator  has  been  in  general 
use,  especially  in  the  eastern  section  of  this  country,  during  the  past 
30  years,  for  the  excavation  and  back  filling  of  large  trenches  for 
waterworks  and  sewer  systems.  It  has  many  admirable  features  and 
is  especially  well-adapted  to  large  sewer  trench  work  in  hard  soils.  A 
trestle  cable  excavator  on  sewer-trench  construction  is  shown  in 
Fig.  70. 

This  type  of  excavating  machine  consists  of  a  series  of  trestles 
supporting  an  overhead  track.  The  trestles  or  bents  are  connected 
by  rods  at  the  bottom  and  by  the  beam  track  at  the  top  and  rest 
upon  a  plank  or  rail  track.  The  operating  machinery  is  carried  by  a 
platform  located  at  one  end  of  the  structure.  The  overhead  track 
supports  several  carriers  which  carry  the  buckets  or  tubs.  The 
whole  framework  is  self-contained  and  can  be  moved  ahead  as  a 
unit  from  one  section  of  the  work  to  another. 

The  trestles  are  made  of  timber  framed  together  to  form  square 
or  A-shaped  bents.     They  are  from  15  feet  to  20  feet  in  height 

424 


EARTHWORK 


125 


and  are  equipped  with  castor  frames,  wheels,  etc.  These  bents 
are  connected  together  at  the  bottom  by  bars  of  tubular  steel  of 
from  1  inch  to  2§  inches  in  diameter.  The  bents  rest  on  T-rails 
which  are  spiked  to  sections  of  planking,  and  enough  track  is  provided 
to  move  the  whole  machine  ahead  100  feet  at  a  time. 

The  track  or  support  for  the  travelers  or  carriers  is  made  up 
of  sections  of  I-beams  or  channels  which  are  bolted  to  or  hung  from 
the  head  blocks  of  the  bents. 


iJlj^ 

J^^ 

1| 

■  MTli^i 

}  am"  ^H  — — -^^^1 

^ 

^ 

s^-:^^§im^ 

IPi^Hgp: vf^!f?S«^^    .:-- 

Fig.  70.     Trestle  Cable  Excavator  ou  8ewer  Treuch  Construction 
Courtesy  of  Carson  Trench  Machine  Company,  Boston,  Massachusetts 


Operating  Equipment.  The  operating  equipment  consists  of 
the  boiler,  engine,  and  car  upon  which  the  machinery  is  placed. 

The  boiler  is  of  the  vertical,  tubular  t\T)e,  and  is  equipped  with 
all  appliances  for  efficient  operation  and  control.  It  is  usually 
operated  at  a  steam  pressure  of  about  100  pounds.  The  engine 
is  a  2-drum,  double-cylinder,  hoisting  machine  with  reversible  link 
motion.  The  drums  are  controlled  by  friction-clutch  brakes;  one 
carries  the  hoisting  rope,  and  the  other  carries  the  endless  rope  which 


425 


126  EARTHWORK 

operates  the  carriers  and  buckets.  The  drums  are  independent, 
and  so  arranged  that  they  may  be  operated  in  unison  or  separately. 
The  boiler  and  engine  are  generally  mounted  on  the  same  bed  plate 
which  is  supported  by  a  platform  mounted  on  rollers  or  wheel  trucks. 
The  front  end  of  the  car  supports  the  head  trestle.  A  suitable 
house  is  usually  built,  in  sections,  over  the  platform  and  may  be 
used  completely  or  partly,  depending  on  climatic  conditions. 

Excavating  Equipment.  The  excavating  equipment  consists 
of  the  tubs,  the  carriers,  and  the  cables. 

Upon  the  overhead  track  run  several  carriages,  travelers,  or 
carriers,  which  are  provided  with  wheels  made  to  fit  the  flanges  of 
the  structural  sections.  From  each  carrier  is  suspended  a  tub  which 
is  equipped  with  an  automatic  catch  and  is  self-dumping  and  self- 
righting.  The  carriers  are  connected  by  a  continuous  rope  which 
is  operated  by  a  drum  on  the  engine,  and  are  raised  and  lowered  by 
hoisting  ropes  controlled  by  a  rope  operated  by  another  drum  on 
the  engine. 

Method  of  Operation.  The  labor  crew  necessary  to  operate 
a  trestle  cable  excavator  consists  of  an  engineer,  a  fireman,  a  latch- 
man,  and  a  tubman.  The  engineer  operates  the  engine  and  has 
general  charge  of  the  work.  The  fireman  supplies  the  boiler  with 
fuel,  and  oils  the  machinery.  The  latchman  operates  the  latches, 
which  release  and  grip  the  tub  lines  for  raising  and  lowering  the 
buckets.  The  tubman  hooks  and  unhooks  the  tubs,  and  has  gen- 
eral charge  of  their  filling  and  emptying. 

The  machine  being  set  up  in  position,  the  engineet*  operates 
the  hoisting  line  and  releases  the  jaw  clutches  on  the  tub  ropes, 
thus  allowing  the  tubs  or  buckets  to  drop  into  the  excavation. 
The  tubs  are  unhooked  and  another  set  of  filled  tubs  hooked  on. 
The  loaded  tubs  are  then  hoisted  up  to  the  locks  on  the  carriers, 
and  the  whole  set  is  moved  to  the  disposal  place  by  the  operation 
of  the  continuous  traversing  line.  Usually  one  section  of  the  trench 
is  being  excavated  while  another  section  is  being  back  filled,  so 
that  the  material  removed  at  the  former  place  can  be  utilized  directly 
in  the  latter.  It  may  be  necessary  at  the  beginning  of  the  work, 
or  in  special  cases  of  crossings,  etc.,  to  dump  the  material  into 
temporary  spoil  banks,  or  into  carts  for  removal  from  the  site.  As 
soon  as  one  section  is  completed,  the  machine  pulls  itself  ahead 


426 


EARTHWORK  127 

by  means  of  a  winch  on  the  engine  and  a  rope  passing  through  a 
snatch  block  attached  to  a  deadman  set  ahead. 

Machines  may  be  had  with  double  and  single  upper  tracks. 
The  nominal  capacity  of  a  double-track  machine  is  50  per  cent 
greater  than  that  of  a  single-track  machine,  as  one  set  of  buckets  is 
being  raised  loaded,  while  the  other  set  is  being  lowered  empty.  Thus 
3  sets  of  buckets  are  continually  in  use,  one  set  being  filled,  one 
hoisted  and  carried  to  the  dump,  and  the  other  dumped  and  returned 
to  be  loaded.  A  double-track  machine  is  more  economical  for 
trenches  over  5  feet  in  width. 

The  average  output  for  a  6-bucket,  single-track  machine  is 
about  125  cubic  yards  for  a  10-hour  day. 

Cost  of  Operation.  The  rental  charge  of  a  6-bucket,  single- 
track  machine  is  about  $200  per  month.  The  cost  of  transportation, 
setting  up,  and  dismantling  will  vary  with  the  distance,  length  of 
haul,  experience  of  men,  etc.,  and  will  range  from  $100  to  $500. 

About  I  ton  of  coal  per  day  will  be  used,  and  the  cost  of  oil, 
waste,  supplies,  etc.,  will  vary  from  $1  to  $5  per  day.  The  net  cost 
of  operation  of  the  machine  would  be  about  $25  per  day.  Assuming 
an  average  output  of  100  cubic  yards,  the  cost  of  the  work  exclusive 
of  sheeting,  pumping,  loosening  of  material  in  trench,  etc.,  would 
be  about  25  cents  per  cubic  yard. 

Field  of  Usefulness.  The  trestle  cable  excavator  is  especially 
adapted  to  the  excavation  of  trenches  for  large  sewers  and  water 
mains  in  hard  soils,  and  in  city  streets.  The  work  is  restricted  to 
the  immediate  area  of  the  trench,  leaving  part  of  the  street  unob- 
structed for  traffic.  The  method  of  operation  is  efficient,  as  the 
excavated  material  is  generally  used  directly  in  back  filling.  The 
method  of  operation  is  also  easy,  simple,  and  safe. 

TRESTLE  TRACK  EXCAVATOR 

Construction.  The  trestle  track  excavator  is  very  similar  in  its 
method  of  operation  to  the  trestle  cable  excavator.  The  principal 
difference  is  the  suspension  of  the  carriers  from  a  car  or  carriage 
which  moves  along  a  track  supported  on  the  tops  of  the  trestles. 

The  construction  consists  of  a  series  of  light,  steel-frame  trestles, 
of  trapezoidal  shape  and  6  feet  in  height,  spaced  about  10  feet  on 
centers.    These  trestles  are  mounted  on  double-flanged  wheels,  which 


427 


128 


EARTHWORK 


run  on  rails.  The  tops  of  the  trestles  are  connected  by  steel  channels 
which  form  a  continuous  track  on  which  the  carriage  runs. 

Operating  Equipment.  The  operating  equipment  consists  of 
a  vertical,  tubular  boiler,  and  a  double-drum  hoisting  engine,  carried 
on  a  car  at  the  forward  end  of  the  machine. 

Excavating  Equipment.  The  excavating  equipment  consists  of  a 
steel-frame  car  supported  on  four  wheels  which  run  upon  the  trestle 


Fig.  71.     Trestle  Track  Excavator 
Courtesy  of  Potter  Manufacturing  Company 


track.  The  car  is  operated  by  cables  which  connect  to  the  hoisting 
engine.  On  the  car  is  a  hoist  which  raises  and  lowers  two  steel 
buckets.  The  buckets  are  made  in  three  sizes:  J-,  §-,  and  1-cubic 
yard  capacities.  A  view  of  a  car  in  operation  is  shown  in  Fig.  71. 
Method  of  Operation.  The  machine  requires  a  crew  of 
3  men;  one  to  operate  the  hoisting  engine,  and  two  to  operate  the 
bucket  hoists  on  the  carriage. 


428 


EARTHWORK  129 

The  carriage  is  moved  by  a  cable  from  the  hoisting  engine 
to  the  place  of  excavation,  where  either  one  or  both  buckets  are 
lowered  into  the  trench,  filled  by  the  laborers  in  the  trench,  and 
raised  above  the  floor  of  the  car.  The  car  is  then  moved  to  the 
place  of  back  fill  or  dump,  where  the  buckets  are  lowered  and  dumped. 

Cost  of  Operation.  The  following  statement  is  given  as  a 
typical  case  of  the  cost  of  excavation  with  a  trestle  track  machine. 

niustrative  Example.  The  trench  had  a  width  of  21  feet  and 
an  average  depth  of  30  feet.  The  material  excavated  consisted 
of  a  shallow  top  la\'er  of  loam,  then  15  feet  of  soft  blue  clay,  6  to 
8  feet  of  stiff  blue  clay,  1  foot  of  sandy  loam,  and  then  about  2  feet 
of  hard  blue  clay.  The  trench  machine  was  equipped  with  6  buckets 
of  J-cubie  yard  capacity,  and  4  were  filled  while  the  remaining  2 
were  being  removed  and  dumped.  The  excavator  removed  the 
lower  12  or  14  feet  of  the  trench. 

The  following  gives  the  cost  of  operation  based  on  an  8-hour  day. 

Operating  Cost  of  Trestle  Track  Excavator 

Labor: 


1  foreman 

$  4.00 

1  engineer 

5.00 

1  fireman 

2.50 

1  car  operator 

3.50 

1  car  helper 

2.00 

20  laborers  in  trench,  @  $2.00 

each 

40.00 

1  laborer  on  dump 

2.00 

Total  labor  cost,  per  day 

$59 .  00 

and  Supplies: 

\  ton  coal,  @  $5.00 

$2.50 

OU,  waste,  etc. 

1.00 

Repairs 

1.50 

Total  fuel  and  supplies 

$5.00 

rat. 

Rent  of  machine,  @  $125  per 

month 

$5.00 

Total  Cost  of  Operation  for  an  8-hour  Day  $69 .  00 

Average  Daily  Excavation  (cu.  yd.)  175 
Unit  Cost  of  Trestle  Track  Excavating,  per  cu.  yd., 

$69.00^175=  00.39 

Field  of  Usefulness.  The  trestle  track  excavator  has  the  same 
scope  and  advantages  as  the  trestle  cable  excavator.  It  is  especially 
efficient  in  trench  excavation  in  congested  city  streets  where  the 


429 


130  EARTHWORK 

demands  of  keeping  at  least  part  of  the  street  open  to  public  traffic 
requires  the  restriction  of  the  work  to  as  limited  an  area  as  possible. 
On  very  wide  trenches,  it  is  advisable  to  use  a  machine  equipped 
with  a  double  track  and  2  cars  in  order  to  facilitate  the  work. 

TOWER  CABLEWAY 

Development.  The  tower  cableway  is  an  excavating,  hoisting, 
and  conveying  device  devised  about  1875  for  slate  quarries  in 
eastern  Pennsylvania.  Then  for  a  period  of  years  the  cableway 
was  used  largely  in  quarry  work  and  logging  operations.  In  more 
recent  times,  this  machine  has  been  adapted  to  the  conveying  of 
materials  on  construction  work,  the  excavation  of  the  hghter  and 
softer  soils,  the  hoisting  and  conveying  of  the  harder  soils  excavated 
by  other  machinery,  etc.  This  article  will  deal  with  the  use  of 
the  cableway  in  trench  construction  only.  A  double  cableway 
on  trench  excavation  is  shown  in  Fig.  72. 

Construction.  The  essential  parts  of  a  tower  cableway  are 
the  towers,  the  cable,  bucket  or  dipper,  carrier,  and  the  power 
equipment. 

The  towers  are  framed  timber  structures  varying  in  height 
with  the  location  and  character  of  the  work.  They  are  either  fixed 
or  anchored  in  position,  or  mounted  on  wheel  trucks  which  run  on 
tracks,  thus  providing  for  the  movement  of  one  or  both  ends  of 
the  cableway.  The  tops  of  the  towers  are  provided  with  saddles 
and  sheaves  for  the  cables. 

Operating  Equipment.  The  operating  equipment  of  a  tower 
cableway  consists  of  a  boiler  and  an  engine. 

The  boiler  is  generally  of  the  vertical,  tubular  type,  and  equipped 
with  the  necessary  accessories  for  operation  at  a  pressure  of  100  pounds. 

The  engine  is  a  2-drum,  double-cylinder  machine,  fitted  with 
reversible  link  motion.  The  drums  are  of  the  friction-brake  type; 
one  for  the  hoisting  rope,  and  the  other  for  the  endless,  traversing 
rope  or  cable.  The  drums  are  so  arranged  as  to  be  operated  together 
or  independently.  The  machinery  is  placed  on  a  housed-in  plat- 
form built  of  timber  and  supported  on  4  car  wheels  which  run  on 
short  sections  of  the  track. 

Excavating  Equipment.  The  excavating  equipment  comprises 
a  traveler,  the  tubs,  buckets  or  skips,  and  the  cables. 


430 


EARTHWORK 


131 


The  main  cable  is  made  of  crucible  steel  and  of  a  diameter 
depending   upon   the   span,   load,   elevation,   etc.     It  passes  over 


the  tops  of  the  towers,  is  anchored  behind  them,  and  is  the  track 
over  which  the  carrier  passes.    The  hoisting  and  traversing  ropes 


431 


132  EARTHWORK 

are  crucible-steel  cables  of  from  |  inch  to  |  inch  in  diameter  and 
extend  from  their  respective  drums  on  the  engine  over  the  sheaves 
at  the  tops  of  the  towers  and  thence  to  the  carrier. 

The  traveler  or  carrier  is  a  wrought-iron  frame  which  carries 
the  sheaves  over  which  pass  the  hoisting  and  traversing  cables 
and  the  fall  block  which  supports  the  tub,  skip,  or  bucket.  The 
carrier  is  provided  with  2  or  more  flanged  wheels  which  run  on  the 
main  cable.  One  or  more  carriers  may  be  used  on  the  same  cable- 
way. 

The  fall  block  of  the  carrier  supports  the  tub  or  skip  which 
is  of  steel  or  w^ood  and  of  widely  varying  capacity.  For  trench  work 
tubs  are  generally  used  and  are  made  of  steel  and  provided  with 
double  bottoms  and  automatic  catches.  When  the  cableway  is 
used  for  direct  excavation,  grab  buckets  or  drag-line  buckets  are 
used  and  require  special  operating  equipment. 

Method  of  Operation.  For  trench  excavation,  a  cableway 
having  a  length  or  span  of  from  200  feet  to  400  feet  is  generally 
used.  The  length  of  excavation  will  be  about  50  feet  shorter  than 
the  distance  between  towers. 

The  labor  crew  required  consists  of  an  engineer,  a  fireman,  a 
signalnian  and  two  or  more  laborei's.  The  engineer  operates  the 
engine  and  has  general  charge  of  the  work.  The  fireman  provides  the 
boiler  with  fuel  and  water,  and  looks  after  the  oiling  of  the  machinery. 
The  signalman  signals  to  the  engineer  for  the  raising  and  lowering 
of  the  bucket  or  tub.  The  laborers  are  used  in  filling  and  in  dumping 
the  tub,  and  in  general  service  about  the  job. 

The  bucket  is  lowered  into  the  trench,  filled  by  the  shovelers, 
and  then  raised  above  the  excavation  by  the  operating  of  the  hoist- 
ing drum,  which  is  thrown  out  of  gear  and  held  by  a  brake.  The 
traversing  line  is  then  operated  and  the  carrier  moved  in  either 
direction  until  the  bucket  is  over  the  place  for  dumping.  Then 
the  bucket  is  lowered  by  means  of  the  brake  band  on  the  hoisting 
drum.  The  material  may  be  used  for  back  fill  in  a  section  of  trench 
where  the  pipe  is  laid  or  dumped  into  a  spoil  bank  or  into  wagons 
for  removal  to  a  distant  place  of  disposal.  A  small  crane  or  derrick 
may  be  used  to  advantage,  adjacent  to  the  excavation,  for  the 
transfer  of  the  buckets  from  the  cableway  to  the  dumping  board 
or  hopper. 

432 


EARTHWORK  133 

Cost  of  Operation.  A  typical  case  of  sewer  trench  construc- 
tion will  be  considered  in  the  following  statement  of  the  cost  of 
excavation  with  a  cableway. 

Illustrative  Examyle.  The  trench  is  12  feet  wide  and  with 
an  average  depth  of  20  feet.  The  soil  varies  from  a  surface  layer 
of  loam  of  2-foot  depth,  through  a  clay  substratum  of  8  feet,  to  a 
hard  gravel  deposit.  The  machine  has  two  30-foot  towers  placed 
300  feet  apart  and  is  equipped  with  1-yard  tubs  or  buckets.  Bracing 
and  sheeting  were  carried  on  at  the  same  time  as  the  excavation, 
and  the  sewer  construction  followed  closely  to  allow  for  back  filling 
at  one  end  of  the  section  with  the  material  from  the  other  end. 

Following  is  an  estimate  of  the  cost  of  excavation  under  average 
working  conditions,  during  a  10-hour  day.  A  crew  of  30  men  are 
required  to  pick  and  shovel  the  material  into  the  buckets  and  the 
average  daily  output  will  be  taken  as  300  cubic  yards. 

Operating  Cost  of  Tower  Cableway 

Labor: 


1  foreman 

$  4.00 

1  engineer 

5.00 

1  fireman 

2.50 

1  signalman 

2.50 

.    2  dumpers,  @  $2 .  00  each 

4.00 

30  laborers,  @  $2 .  00  each 

60.00 

Total  labor  expense,  per  day 

$78.00 

Fuel  and  Supplies: 

i  ton  coal,  @  $5 .  00 

$2.50 

Oil,  waste,  etc. 

1.00 

Repairs 

1.50 

Total  Fuel  and  Supplies 

$5.00 

General  and  Overhead  Expenses: 

Interest  (6%  of  $8000)* 

$2.40 

Depreciation  (10%  of  $8000)* 

4.00 

Incidental  expenses 

2.60 

Total  general  expense 

$9.00 

Total  Cost  of  Operation  for  a  10-hour  Day  $92 .  00 

Total  Output  for  a  10-hour  Day  (cu.  yd.)  300 

Unit  Cost  of  Tower  Cableway  Excavating,  per  cu.  yd.  of  material 

handled,  $92.00^300=  00.030 

Unit  Cost  of  Hoisting,  Conveying,  and  Dumping  (excluding  pick 

and  shovel  labor),  per  cu.  yd.  of  material  handled,  $29 .00-^300  =    00 .  097 


♦Based  upon  200  working  days  in  a  year  and  a  10-year  life. 

433 


134  ^        EARTHWORK 

Field  of  Usefulness.  The  cableway  excavator  has  a  wide  and 
important  field  of  usefulness.  It  is  especially  efficient  in  the  handling 
of  materials  across  large  waterways,  valleys,  quarries,  pits,  etc., 
where  surface  transportation  would  be  difficult  and  very  expensive. 
In  the  excavation  of  large  quarries,  gravel  pits,  surface  mines,  dam 
foundations,  reservoirs,  etc.,  the  cableway  can  be  used  as  a  tower 
excavator  directly  or  to  convey  skips,  tubs,  or  buckets  which  con- 
tain the  material  previously  excavated  by  other  machines.  The 
same  cableway  can  of  course  be  used  for  the  transportation  of 
concrete,  stone,  timber,  and  other  building  materials,  as  well  as 
tools,  men,  etc.,  during  the  construction  work  which  follows  the 
excavation. 

The  cableway  can  be  satisfactorily  used  in  trench  excavation 
when  the  excavation  is  of  large  extent,  generally  over  6  feet  in  width 
and  10  feet  in  depth.  With  the  use  of  this  type  of  excavator,  the 
weight  of  the  machinery  is  largely  concentrated  at  the  ends  of  the 
trench,  the  cable  is  at  a  considerable  height  above  the  work  and 
allows  space  for  storage,  handling  of  materials,  etc.  The  principal 
objection  to  the  use  of  the  cableway  on  trench  work  is  its  lack  of 
lateral  control.  It  is  almost  impossible  to  avoid  the  swinging  of 
the  buckets  during  the  raising  and  lowering,  and  this  is  liable 
to  result  in  some  displacement  of  and  damage  to  the  sheeting, 
forms,  etc. 

TILE=TRENCH  TYPES 

General  Features.  Preceding  the  year  1900,  trench  excavation 
for  drain  tile  was  made  largely  by  hand.  With  the  rapid  and  extensive 
development  of  agricultural  drainage  through  the  South  and  Middle 
West,  came  the  use  of  machinery  to  economically  and  expeditiously 
perform  the  great  amount  of  excavation  work  required  by  the 
construction  of  drainage  systems.  At  the  present  time,  there  are 
several  makes  of  trench  excavators,  which  are  especially  adapted 
to  tile-trench  excavation. 

The  essential  parts  of  tile-trench  excavators  are  practically 
the  same  as  for  the  water  and  sewer-pipe  trench  machines,  described 
under  Pipe-Trench  Types.  There  is  one  make  of  machine  which 
has  been  specially  devised  for  the  laying  of  the  tile  as  well  as  for 
the  excavation  of  the  trench.  A  description  of  this  machine  will 
follow. 


434 


EARTHWORK  135 

HOVLAND  TILE  DITCHER 

Power  Equipment.  The  Hovland  tile  ditcher  is  made  in 
two  sections :  a  front  platform  w^hich  carries  the  power  equipment, 
and  a  rear  platform  which  carries  the  excavating  chain.  Both 
platforms  are  made  of  a  steel  framework  supported  on  two  large 
caterpillar  tractors.  Fig.  73  shows  a  general  view  of  the  Hovland 
tile  ditcher. 

It  \Aill  be  noticed  that  the  forward  tractor  carries  the  power 
equipment  which  consists  of  a  vertical,  3-cylinder  gasoline  engine. 
The  main  shaft  of  the  engine  is  connected  by  sprocket  chains  to 
the  driving  shafts  of  the  excavating  belt  of  the  tractions,  and  of 
the  belt  conveyor. 


Fig.  73.     View  of  Hovland  Tile  Ditcher 
Courtesy  of  St.  Paul  Machinery  Manufacturing  Company,  St.  Paul,  Minrtesota 

Excavating  Equipment.  The  excavating  equipment  is  carried 
on  the  rear  platform  and  consists  of  an  excavating  chain  and  its 
supporting  framework. 

The  excavating  chain  is  made  up  of  two  continuous  chains 
which  carry  an  endless  set  of  hinged  links.  To  the  vertical  sections 
of  these  links  are  bolted  the  knives  or  cutters  of  any  width  from 
5  inches  to  30  inches.  The  links  are  hinged  in  such  a  way  that 
when  a  cutter  strikes  a  stone  or  other  obstruction  in  a  trench,  the 
chain  gives,  and  the  cutter  slides  over  the  obstruction  without 
injury.  An  automatic  cleaning  device  consisting  of  a  projecting 
arm,  is  placed  above  the  upper  end  of  the  chain  and  scrapes  over 

435 


136 


EARTHWORK 


the  surface  of  each  bucket  as  it  passes.  The  excavated  material 
is  thus  removed  from  the  buckets  and  falls  upon  a  moving  belt  con- 
veyor which  is  located  under  the  excavating  chain  at  its  upper  end. 

The  framework  which  supports  the  excavating  chain  is  shown 
in  Fig.  74.  It  comprises  a  small,  upper  wheel  and  a  large,  lower 
wheel,  or  drum,  about  which  the  chain  revolves.  The  lower  wheel 
is  suspended  by  chains  from  the  rear  of  the  frame  and  can  be  raised 
and  lowered  by  a  gear-operated  shaft.  The  upper  wheel  is  on  a 
shaft  which  is  chain-driven  from  the  engine  located  on  the  forward 
platform. 

An  adjustable  steel-frame  curbing  can  be  fastened  to  the  rear 
of  the  excavating  tractor  and  drawn  along  the  completed  trench. 


Fig.  74.     Excavating  Wheel  and  Frame  of  Hovland  Tile  Ditcher 
Courtesy  of  St.  Paul  Machinery  Manufacturing  Company,  St.  Paul,  Minnesota 

This  curbing  can  be  adjusted  to  the  width  of  the  trench  and  made 
high  enough  to  project  above  the  ground  surface.  A  steel  spout 
is  placed  on  the  inner  and  curved  portion  and  as  the  machine  pro- 
gresses, a  man  places  a  tile  in  at  the  top  of  the  spout,  which  is  curved 
so  as  to  allow  the  tile  to  slide  out  in  place  along  the  bottom  of  the 
finished  trench. 

Method  of  Operation.  A  crew  of  3  or  more  men  are  necessary 
to  properly  operate  a  tile-trench  excavator:  an  engineer  who  has 
charge  of  the  operating  equipment,  an  operator  who  manipulates 
the  excavating  wheel,  a  tile  layer  and  one  or  more  laborers  to  supply 


436 


EARTHWORK  137 

fuel,  water,  and  supplies  for  the  machine  and  for  general  service 
about  the  work. 

The  revolution  of  the  excavating  chain  or  wheel  brings  a  series 
of  knives  or  buckets  into  contact  with  the  soil  and  each  bucket 
removes  a  slice  of  earth,  which  is  dumped  upon  the  belt  conveyor 
and  carried  to  the  spoil  bank,  at  the  sides  of  the  trench.  The 
operator  lowers  the  wheel  or  chain  into  the  soil  as  the  excavation 
proceeds  and  governs  the  depth  by  a  sight  rod,  placed  on  the  machine. 
As  soon  as  the  required  depth  is  reached  the  engineer  sets  the  tractor 
chain  in  motion  and  the  machine  moves  ahead  to  the  next  position. 

With  the  Hovland  tile  ditcher  the  drain  tile  can  be  laid  as 
the  excavation  is  completed,  by  placing  the  tile  in  the  curb  which 
follows  directly  behind  the  excavating  chain.  Fig.  74.  It  is 
often  necessary  to  reset  the  tile  after  it  leaves  the  curb  in  order 
to  secure  proper  alinement  and  close-fitting  joints. 

One  manufacturer  has  devised  a  longitudinal  belt  conveyor, 
which  carries  the  excavated  material  to  a  point  behind  the  machine 
and  dumps  it  back  into  the  trench.  This  device  has  not  been 
satisfactory  because  it  does  not  allow  enough  time  after  the  exca- 
vation for  the  placing  of  the  tile. 

Cost  of  Operation.  An  approximate  estimate  of  the  capacity 
and  cost  of  operation  of  a  tile  ditcher  will  be  given  in  the  following 
statement. 

Illustrative  Example.  A  trench  machine  has  a  gasoline  power 
equipment  and  an  excavating  chain  or  wheel  capable  of  digging 
a  trench  14|  inches  wide  and  4J  feet  deep.  The  soil  is  loam  and 
clay  with  gumbo  in  places.  The  average  depth  of  cut  is  4 J  feet, 
and  the  average  progress  is  1300  feet  per  10-hour  day. 

Operating  Cost  of  Tile  Ditcher 

Labor: 


$14.00 


Total  fuel  and  supply  cost  $2 .  50 

437 


1  operator,  @  $125  per  month 

1  fireman 

1  helper 

1  team  and  driver 

$5.00 
2.00 
2.00 
5.00 

Total  labor  cost,  per  day 

Fml  and  Supplies: 

10  gallons  gasoline,  @  20c 
Oil,  waste,  etc. 

$2.00 
.50 

138  EARTHWORK 

General  and  Overhead  Expenses: 

Interest  (6  %  of  $5200)  *  $2 .  00 
Depreciation  (12^  %  of  $5200)  *  4 .  25 

Repairs  and  incidentals  2 .  75 


Total  general  expense  $9.00 


Total  Operating  Cost  per  10-hour  Day  $25 .  50 

Average  Progress  per  Day  (ft.)  1300 

Average  Daily  Excavation  (cu.  yd.)  260 

TT  -^  r^    ^    <•  rr-i    rp        uTT  4.-  fper  f t.  $25.50"^  1300  00.019 

Unit  Cost  of  Tile-Trench  Excavating     <^  jd^occn    o^^         n/^  «r.o 

^     (per  cu.  yd.  $25.50-^260         00.098 

Field  of  Usefulness.  The  tile-trench  excavator  is  a  very 
efficient  and  practicable  machine  for  ordinary  soil  conditions  in 
fairly  level  land  with  few  obstructions.  Where  the  soil  is  low  and 
wet,  the  machine  must  be  supported  on  caterpillar  tractors  to 
distribute  the  weight  over  the  soft  soil.  Where  obstructions  such 
as  large  stones,  roots,  etc.,  abound,  a  large  amount  of  extra  hand 
labor  is  required. 

For  work  of  considerable  magnitude,  the  tile  ditcher  can  exca- 


*  Based  on  150  days  per  year  and  an  8-year  life. 


438 


REVIEW  QUESTIONS 


439 


REVIEW  QUESTIONS 

ON  THE  SUBJECT  OF 

RAILROAD  ENGINEERING 

PART  I 


1.  What  are  the  elements  of  railroad  location  which  are  in 
general  antagoni.^tic?  Deduce  from  the  above  the  chief  duties  of 
the  locating  engineer. 

2.  What  is  the  chief  object  to  be  accomplished  by  a  recon- 
noissance  survey? 

3.  What  are  the  three  elements  involved  in  the  survey  of 
any  line  and  what  are  the  methods  of  determining  these  elements 
in  reconnoissance  surveys? 

4.  What  is  the  practical  value  and  what  are  the  limitations 
of  barometric  leveling? 

5.  What  is  the  general  object  to  be  accomplished  by  means 
of  a  preliminary  survey? 

6.  To  what  extent  should  the  compass  needle  be  used  dur- 
ing preliminary  surveys? 

7.  Why  is  it  that  a  Locke  level  with  its  limited  accuracy  is 
a  proper  instrument  for  cross-section  work? 

8.  Under  what  circumstances  is  the  stadia  method  advan- 
tageous for  preliminary  surveys? 

9.  What  is  the  justification  of  making  two  or  more  pre- 
hminary  surveys  through  difficult  portions  of  the  route? 

10.  How  are  the  tangents  and  curves  for  the  "location" 
determined?  How  is  the  location  survey  ''tied"  to  the  prelim- 
inary survey? 

11.  How  would  you  select  a  low-grade  line  through  a  difficult 
piece  of  mountainous  country? 

12.  How  are  transit  stations  and  bench  marks  secured 
against  disturbance  during  construction  of  the  road? 

441 


RAILROAD  ENGINEERING 

13.  Define  the  degree  of  a  curve.  What  is  the  approximate 
rule  for  the  radius  of  a  curve  of  a  given  degree  'i  What  is  the 
percentage  of  error  of  this  rule  for  a  10°  curve  ? 

14.  What  is  a  sub-chord  ?  What  will  be  the  excess  length 
of  a  sub-chord  with  a  nominal  length  of  45'  on  a  S'^  curve? 

15.  What  is  the  difference  between  the  nominal  length  of  a 
railroad  curve  and  its  true  length  measured  on  the  arc  ?  What 
will  this  amount  to  in  the  case  of  a  6°  curve  subtending  a  central 
angle  of  34°  30'? 

16.  If  two  adjacent  tangents  which  make  an  angle  of  24°  16, 
are  connected  by  a  3°  30'  curve,  what  will  be  the  distance  from  the 
vertex  to  the  point  of  the  curve  ? 

17.  In  the  case  given  above,  how  far  will  the  curve  pass 
from  the  vertex  ? 

18.  A  3°  30'  curve  is  to  begin  at  Sta.  142  +  65  and  is  to 
have  a  total  central  angle  of  28°  30'  ;  compute  the  deflections  from 
the  tangent  at  the  P.C.  to  each  station  and  to  the  P.T. 

19.  In  the  above  case  assume  that  on  account  of  obstructions 
to  sighting  it  was  necessary  to  set  up  the  instrument  at  Sta.  147 
and  sight  back  to  Sta.  144.  Applying  the  rule  of  section  25,  what 
should  be  the  reading  of  the  horizontal  plate  when  the  instrument 
is  sighted  at  Sta.  144,  and  what  should  be  the  reading  when  it  is 
sighted  ahead  at  Sta.  148  ? 

20.  Assume  that  a  3°  curve  having  a  central  angle  of  14°  30 
is  to  be  located  by  tangential  offsets;  make  a  sketch  of  this  case 
and  compute  and  mark  on  the  sketch  the  deflections  and  distances. 

21.  After  running  a  4°  curve  to  some  point  n  as  in  Figure 
16,  the  curve  is  found  to  be  obstructed.  It  is  estimated  that  the 
curve  would  again  be  clear  about  400  fett  further  on.  Compute 
the  long  chord  nvi  and  the  angle  which  7i?7i  would  make  with  a 
tangent  to  the  curve  at  n.  What  would  be  the  offset  from  this 
long  chord  to  the  second  station  beyond  n'^ 

22.  Give  detailed  solutions  of  the  problems  stated  in  sec- 
tion 30  ? 

23.  Give  detailed  solutions  of  the  problems  stated  in  sec- 
tion 34  ? 

24.  What  is  the  essential  character  of  a  transition  curve  and 
why  it  is  necessary  ? 

442 


REVIEW  QUESTIONS 

ON  THE  SUBJECT  OF 

RAILROAD  ENGINEERING 

PART  II 


1 .  What  is  the  chief  cause  of  the  deterioration  of  locomotive 
boilers  due  to  impure  water  supply? 

2.  What  are  the  chief  difficulties  encountered  in  the  construc- 
tion of  engine  houses  and  how  are  the  difficulties  met? 

3.  What  elements  must  be  considered  in  computing  the  total 
cost  of  any  kind  of  railroad  tie? 

4.  What  is  the  preferable  method  of  locating  ties  with  refer- 
ence to  rail  joints? 

5.  Assuming  that  an  85-pound  rail  and  a  70-pound  rail  have 
similar  cross-sections,  what  is  the  relative  stiffness? 

6.  What  are  the  elements  of  a  perfect  rail  joint  and  why  is  it 
impossible  to  produce  a  perfect  rail  joint  for  steam  railroad  work? 

7.  Why  are  plain  smooth  spikes  preferable  to  spikes  wkich 
are  jagged? 

8.  What  are  the  three  principles  which  form  the  basis  of  the 
design  of  nut  locks? 

9.  Give  a  brief  statement  of  the  general  methods  of  obtaining 
a  pure  water  supply. 

10.  What  are  the  elements  of  an  ideal  form  of  ballast?  What 
the  disadvantages  of  *'mud"  ballast?  What  are  the  advantages  of 
stone  ballast? 

11.  What  are  the  causes,  other  .than  mere  decay  of  the  wood, 
which  require  that  ties  should  be  renewed? 

12  What  are  the  features  of  the  A.  S.  C.  E.  rail  section  which 
are  constant  for  all  weights  of  rails  and  what  are  the  proportions 
which  are  constant  or  nearly  constant? 

13.  What  are  the  advantages  and  disadvantages  in  using 
very  long  rails? 

443 


RAILROAD  ENGINEERING 

14.  What  are  the  advantages  obtained  by  the  use  of  tie 
plates? 

15.  How  many  track  bolts  in  a  mile  of  single  track  using  six- 
bolt  splice  bars  and  30-foot  rails? 

16.  How  much  is  allowed  for  rail  expansion  and  how  is  this 
practically  provided  for? 

17.  How  much  gap  would  you  allow  at  a  rail  joint  when  the 
temperature  of  the  rail  at  the  time  of  laying  is  45°  F? 

18.  What  should  be  the  middle  ordinate  of  a  30-foot  rail  bent 
to  a  40°  curve? 

19.  What  would  be  the  superelevation  of  the  outer  rail  for  a 
60°  curve  when  the  maximum  speed  is  45  miles  per  hour? 

20.  If  the  maximum  speed  for  trains  is  assumed  at  60  miles 
per  hour,  what  will  be  the  length  of  a  string  or  tape  which,  when 
stretched  as  a  chord  inside  the  rail,  will  give  a  middle  ordinate 
equal  to  the  required  superelevation? 

21.  What  is  the  fundamental  advantage  of  a  point  switch 
over  a  stub  switch? 

22.  Suppose  it  were  required  to  make  to  order  a  frog  having 
a  frog  angle  of  6°  30';  what  would  be  the  frog  number? 

23.  Verify  the  calculations  for  the  length  of  the  lead  of  a 
switch  from  a  straight  track  using  a  No.  8  frog  on  the  basis,  first, 
of  circular  lead  rails,  and  second,  of  straight  point  rails  and  straight 
frog  rails,  using  the  values  given  in  Table  III. 

24.  If  a  No.  8  frog  has  been  used  in  switching  from  a  straight 
track,  what  will  be  the  radius  of  the  connecting  curve  when  the 
distance  between  track  centers  is  13  ft.? 

25.  What  will  be  the  length  and  radius  of  the  connecting 
curve  running  from  a  switch  on  the  outside  of  a  main  track,  which 
is  a  4°  30'  curve,  the  frog  used  being  No.  9  and  the  distance  between 
the  track  centers  13  ft.? 

26.  Make  all  the  computations  for  the  location  of  a  turnout 
to  the  inside  of  a  4°  curve  using  a  No.  8  frog. 

27.  What  are  the  different  kinds  of  tracks  making  up  a  freight 
yard? 

28.  By  what  device  is  engine  service  economized  in  planning 
a  freight  yard? 


444 


REVIEW  QUESTIONS 

ON  THE  SUBJECT  OF 

RAILROAD  ENGINEERING 

PART  III 


1.  Discuss  the  two  classes  of  financial  interests  in  the 
ownership  of  railroads — the  security  and  profits  of  each. 

2.  Describe  methods  of  estimating  the  probable  volume 
of  traffic  on  a  proposed  road. 

3.  Discuss  the  division  of  the  gross  revenue  and  the  per- 
centages spent  in  operating  expenses,  fixed  charges,  and  dividends. 

4.  Discuss  operating  expenses  per  train-mile;  their  uni- 
formity for  heavy  and  light  traffic  roads;  the  tendency  toward 
variation  of  the  chief  items. 

5.  Discuss  the  relation  of  railroad  rates  to  railroad  expenses. 

6.  Explain  why  a  reduction  in  distance  is  profitable  when 
handling  competitive  business,  but  unprofitable  when  handling 
non-competitive  business. 

7.  Discuss  curve  compensation;  the  reasons  for  its  use: 
the  values  which  should  be  employed. 

8.  Explain  the  distinction  between  minor  and  ruling  grades. 

9.  What  is  the  meaning  of  'Velocity  head"?  What  is  the 
velocity  head  of  a  train  when  moving  at  the  following  velocities 
in  miles  per  hour:  21;  27.4;  32.25?  What  velocities  correspond  to 
velocity  heads  of  18.58;  38.92;  49.25? 

10.  Explain  the  fundamental  principle  of  a  virtual  profile, 
and  describe  its  use  and  possible  misuse. 

11.  Classify  train  resistances,  with  a  brief  discussion  of  each 
class  or  kind, 

12.  How  much  additional  tractive  force  per  ton  will  be 
necessary  to  increase  the  velocity  of  a  train  from  8  m.p.h.  to  22 
m.p.h.  in  a  distance  of  800  feet? 


445 


RAILROAD  ENGINEERING 

13.  Assume  that  an  engine  weighs  * 253,000  pounds  and 
that  its  cylinder  tractive  power  at  M  velocity  is  33,778  pounds, 
what  is  its  rating  for  a  1.1  per  cent  grade? 

14.  How  many  cars  (empties)  each  weighing  17  tons,  could 
be  hauled  up  that  grade? 

15.  On  the  basis  of  a  Mikado  locomotive,  with  220,000 
pounds  on  the  drivers,  weighing  435,000  pounds,  including  tender, 
total  heating  surface  4720  square  feet,  besides  a  superheater, 
boiler  pressure  170  pounds,  using  4000  pounds  of  coal  per  hour, 
whose  effective  B.t.u.  is  11,500,  cylinders  28  inches  in  diameter 
and  32  inches  stroke,  drivers  63  inches  diameter: 

(a)  What  is  the  maximum  velocity  (M)  at  which  full  pres- 
sure of  steam  may  be  maintained?     , 

(b)  What  will  be  the  cylinder  tractive  power  and  the  draw- 
bar pull  at  M  velocity? 

(c)  What  willbe  the  cylinder  tractive  power  at  a  velocity 
of  20  m.p.h.? 

(d)  Draw  the  curves  for  cylinder  tractive  power  and  draw- 
bar pull  for  all  velocities  up  to  35  miles  per  hour. 

(e)  Assuming  a  train  of  20  freight  cars  averaging  68  tons 
and  a  caboose  weighing  12  tons,  what  is  the  maximum  rate  of 
speed  which  could  be  maintained  on  a  0.7  per  cent  grade? 

(f)  Draw  the  speed  curve  for  acceleration  from  starting  to 
maximum  speed  for  this  train  and  grade. 

16.  Demonstrate  the  fundamental  principle  in  the  economy 
of  pusher  grades. 

17.  Given  a  maximum  grade  of  2.10  per  cent,  what  would  be 
the  corresponding  through  grade  if  one  pusher  engine  is  used — 
the  engine  being  of  the  type  described  in  Question  15?  If  two 
pushers  were  used  on  the  2.10  per  cent  grade,  what  would  be  the 
corresponding  one-pusher  and  through  grades? 

18.  Discuss  the  elements  of  the  cost  of  the  operation  of 
pusher  engines. 

19.  Discuss  the  fundamental  principles  of  the  ''balance  of 
grades  for  unequal  traffic". 

20.  Assume  that  an  investigation  showed  a  3:1  ratio  in 
east-bound  and  west-bound  traffic.  On  the  basis  of  a  0.7  per 
cent  grade  against  east-bound  traffic  and  the  use  for  both  through 
and  pusher  work  of  engines  of  the  type  described  in  Question  15, 
what  would  be  the  corresponding  grade  against  west-bound  traffic? 

446 


REVIEW  QUESTIONS 

ON  THE  SUBJECT  OF 

EARTHWORK 

PART  I 


1.  State  the  different  classes  of  power  shovels. 

2.  How  would  you  excavate  a  canal  200  feet  wide  and  15 
feet  deep? 

3.  Compute  the  time  and  cost  of  excavation  with  a  |-yard 
revolving  shovel  of  a  basement  excavation,  200  feet  long,  60  feet 
wide,  and  10  feet  deep,  in  a  sandy  clay  soil. 

4.  How  many  cubic  yards  of  loam  and  clay  can  one  laborer 
loosen  from  a  pit  5  feet  deep  and  shovel  into  1  J-yard  dump  wagons 
in  a  9-hour  day? 

5.  Compute  the  cost  of  operation  of  a  2-yard  drag-line 
excavator  on  an  irrigation  can^l  in  glacial  clay  and  requiring  the 
removal  of  about  2500  cubic  yards  per  100  feet. 

6.  What  is  the  most  efficient  method  of  supporting  an 
excavator  on  soft  wet  soils? 

7.  Describe  the  method  of  operation  of  an  elevating  grader. 

8.  Give  an  analytical  statement  showing  the  relative 
economy  of  hand-  and  power-shovel  excavation. 

9.  Discuss  the  factors  which  determine  the  method  to  be 
used  in  excavation. 

10.  Discuss  the  relative  efficiencies  of  four  types  of  scrapers. 

11.  State  the  advantages  of  electric  operation  of  a  power 
shovel. 

12.  What  is  the  drag-line  principle? 

13.  Describe  a  machine  which  can  excavate  a  canal  to  a 
true  grade  and  with  smooth  side  slopes. 

14.  Describe  and  illustrate  by  a  diagram  the  operation  of  a 
double-tower  excavator. 


447 


EARTHWORK 

15.  Describe  the  different  tools  and  methods  of  loosening 
earth. 

16.  Describe  the  method  of  grading  up  an  earth  road  with 
a  blade  grader. 

17.  What  are  the  relative  advantages  of  blade  and  elevating 
graders  in  earth-road  construction? 

18.  Describe  the  method  of  operation  of  a  steam  shovel  of 
the  fixed-platform  type. 

19.  Describe  the  most  economical  power  equipment  to  use 
on  a  drag-hne  excavator  operating  on  a  canal  in  the  Middle  West, 
twenty  miles  from  a  railroad. 

20.  What  are  the  special  fields  of  usefulness  of  the  small 
revolving   shovels? 

21.  Describe   the   various   types   of   hand   shovels. 

22.  What  type  of  dredge  would  you  use  on  a  job  where  there 
were  several  canals  to  be  dug  in  the  same  locality? 

23.  Describe  the  machine  which  can  be  most  economically 
used  for  the  excavation  of  small  ditches  in  favorable  soils. 

24.  Describe  the  walking  equipment  of  a  walking  drag-line 
excavator. 

25.  Discuss  the  relative  efficiency  of  different  types  of 
excavators  in  shallow  earth  excavation. 


448 


REVIEW  QUESTIONS 

ON  THE  SUBJECT  OF 

EARTHWORK 

PART  II 


1.  What  are  the  principal  fields  of  usefulness  of  a  hydraulic 
dredge? 

2.  Compute  the  cost  per  foot  of  trench  excavation  and 
tile  laying  for  12-inch  tile  at  a  depth  of  5  feet. 

3.  Can  a  hydraulic  dredge  excavate  hard  materials? 

4.  What  are  the  different  classes  of  dipper  dredges? 

5.  Describe   a   ditcher   which   can  excavate   a   trench   and 
lay  tile. 

6.  Describe  the  operation  of  a  Lobnitz  rock  cutter. 

7.  Describe   the   most   efficient   operating  equipment   of   a 
dipper  dredge. 

8.  Why  has  the  ladder  dredge  not  become  a  more  generally 
used  excavator  in  this  country? 

9.  Discuss  the  relative  merits  of  three  different  makes  of 
continuous  bucket  excavators. 

10.  What  are  the  fields  of  usefulness  of  the  tower  cableway? 

11.  Describe  the  method  of  operation  of  a  ladder  dredge. 

12.  What  kind  of  side  spuds  are  the  most  satisfactory  for 
dredge  operation  in  narrow  canals? 

13.  Describe  the  continuous  bucket  excavator. 

14.  How  are  high  banks  excavated  with  a  ladder  dredge? 

15.  Illustrate  and  describe  the  section  of  a  ditch  which  a 
dipper  dredge  can  excavate. 

16.  What  is  the  best  form  of  excavator  to  use  in  the  excavation 
of  large  trenches  in  narrow  city  streets?     Why? 

17.  Describe  three  types  of  buckets. 

18.  Describe  the  operating  equipment  of  a  hydraulic  dredge. 

449 


EARTHWORK 

19.  What  method  of  subaqueous  rock  excavation  is  used  in 
this  country? 

20.  When  should  electric  operation  be  used  on  a  hydraulic 
dredge? 

21.  How  would  you  operate  traveling  derricks  on  trench 
excavation? 

22.  Describe  the  method  of  operation  of  the  trestle  track 
excavator. 

23.  Compare  the  relative  efficiency  and  scope  of  work  of 
the  Lobnitz  rock  cutter  and  the  drill  boat. 

24.  State  the  different  classes  of  trench  excavators. 

25.  Discuss  the  field  of  usefulness  of  the  dipper  dredge. 


450 


INDEX 


451 


INDEX 


The  page  numbers  of  this  volume  will  he  found  at  the  bottom  of  the  jtages; 
the  numbers  at  the  top  refer  only  to  the  section. 


Page 

Page 

A 

Curves  (continued) 

Abutments 

103 

simple 
transition 

26 
43 

B 

vertical 

57 

Ballast 

124 

amount 

126 

D 

broken  stone 

125 

Dipper  dredge 

377 

cinders 

125 

Distance 

231 

cost 

126 

effect  on  receipts 

232 

gravel 

125 

relation  to  rates  and  expenses 

231 

laying 

126 

Ditches 

61 

mud 

124 

Dredges 

344 

shells,  fine  coals,  etc. 

125 

excavators,  dry-land 

344 

slag 

125 

excavators,  floating 

rock  breakers,  subaqueous 

377 

408 

C 

Dry-land  excavators 

344 

Cattle  guards 

121 

drag-line,  walking 

373 

Cattle  passes 

112 

revolving 

348 

Coaling  stations 

120 

scoop,  walking 

370 

Compound  curves 

39 

scraper,  stationary 

344 

definition 

3^ 

templet 

358 

location,  modifications  of 

41 

tower 

367 

two  branches,  mutual  relations  of    40 

wheel 

362 

Construction,  earthwork 

59 

Constructive  earthwork 

83 

E 

Continuous  bucket  excavator 

418 

Earthwork 

301 

Corbels 

104 

excavations,  methods  of 

301 

Crossings 

170,  171 

principle 

301 

Culverts 

110 

scope 

301 

cattle  passes 

112 

Earthwork  construction 

59 

old-rail 

112 

details,  constructive 

61 

pipe 

110 

roadbed,  width  of 

61 

Curvature 

235 

slopes  and  cross-sections 

59 

compensation 

236 

Earthwork,  constructive 

83 

limitations 

239 

blasting 

83 

operating  disadvantages 

235 

classification 

87 

Curves 

embankments,  formation  of 

86 

compound 

39 

excavating 

83 

Note. — For  page  numbers  see  fool  of  pages. 


453 


INDEX 


Page 

Page 

Earthwork — surveys 

63 

Fresno  grader 

305 

problem,  nature  of 

63 

Frogs 

149 

slope  stakes,  position  of 

63 

volume,  computing  the 

66 

G 

Economics  of  railroad  engineering 

213 

Grade 

241 

curvature 

235 

accelerated  motion,  laws  of 

242 

distances 

231 

minor  and  ruling,  distinction  be- 

finances, railroad 

213 

tween 

241 

grade 

241 

profile,  virtual 

245 

location 

229 

use,     value,     and     possible 

resistances 

252 

misuse  of 

249 

Economic  location 

229 

Graders 

310 

economic  calculations,  reliability 

elevating 

314 

and  value  of 

229 

four-wheel  blade 

310 

general  principles 

229 

reclamation 

311 

Electric  shovels 

339 

two-wheel  blade 

310 

advantages 

339 

equipment 

339 

H 

usefulness 

340 

Engine  houses 

120 

Hovland  tile  ditcher 

435 

Engine  yards 

178 

Hydraulic  dredge 

402 

Excavations  in  earthwork,  methods  of  301 

electric  power 

404 

dredges 

344 

I 

excavators,  trench 

412 

graders 

310 

Interlocking 

195 

hand,  details  of 

302 

scrapers,  drag  and  wheel 

304 

L 

shovels,  power 

318 

Ladder  dredge 

388 

Lobnitz  rock  cutter 

408 

F 

Location  surveys 

24 

Floating  excavators 

377 

methods 

25 

dredge,  dipper 

377 

route,  selecting  a 

24 

dredge,  hydraulic 

402 

Locomotives 

dredge,  ladder 

388 

acceleration,  speed  curves 

280 

Framed  trestles 

100 

drifting 

285 

abutments 

103 

oil-burning 

262 

form,  general 

100 

power  calculations           266,  273, 

,287 

foundations 

101 

rating  of 

257 

multiple-story 

101 

relation  of  type  to  service  and 

Freight  yards 

174 

to  track  conditions 

263 

accessories 

177 

retardation,  speed  curves 

284 

cranes 

178 

route,  selection  of 

288 

scales,  track 

177 

tractive  force  at  higher  velocities  272 

connection  with  main  tracks 

176 

tractive  power,  effect  of  grade  on 

278 

engine  yards 

178 

tractive  power,  relation  of  boiler 

minor 

177 

power  to 

274 

principles,  general 

174 

types  of 

261 

Note. — For  page  numbers  see  foot  of  pages. 


454 


INDEX 


Page 

Page 

N 

Railroad  finances 

213 

Nut  locks 

138 

capitalization 

213 

O 

charges,  fixed 

222 

Old-rail  culverts 

112 

equipment,  maintenance  of 

228 

expenses,  operating 

223 

P 

classification 

225 

Pile  driving 

98 

expenses,  transportation 

228 

Pile  trestles 

98 

monopoly 

219 

Pipe  culverts 

110 

revenue,  gross 

216 

Pipe-trench  excavators 

414 

diversion 

220 

bucket,  continuous 

418 

revenue,  net 

222 

cable,  trestle 

424 

stocks  and  bonds 

214 

cable  way,  tower 

430 

ways  and  structures,  maintenance 

derrick,  traveling 

414 

of 

225 

track,  trestle 

427 

Railroad  surveys 

11 

Power  shovels 

317 

interests,  conflicting 

11 

classification 

317 

principles,  general 

11 

cost,  operating 

337 

Reconnoissance  surveys 

12 

electric 

339 

elements 

13 

steam,  revolving 

337 

existing  maps,  utilization  of 

13 

efficiency  and  economy           34] 

L-344 

grades,  low  ruling 

17 

fixed-platform 

318 

methods 

13 

revolving-platform 

332 

problem,  essential 

12 

Preliminary  surveys 

19 

Resistances 

252 

cross-section  method 

19 

grades  for  unequal  traffic,   1 

bal- 

object,  general 

19 

ance  of 

296 

party  required 

22 

principles 

296 

re-surveys 

23 

relative  traffic,  estimation  of 

298 

stadia  method 

21 

theoretical     balance,     computa- 

Pusher grades 

289 

tion  of 

297 

economy,  general  principles  of 

289 

grades,  pusher 

289 

engines,  operation  of 

291 

train 

252 

length  of 

292 

locomotives,  rating  of 

257-289 

pusher-engine  service,  cost  of 

293 

locomotives,  types  of 

261 

services,  balance  of  grades  for 

290 

operation,  units  of 

259 

tractive     power,     effect 

of 

R 

grade  on 

278 

Rails 

130 

Revolving  excavator 

348 

length 

133 

weight 

131 

Rail  braces 

136 

S 

Rail  joints 

133 

insulated 

135 

Scrapers,  drag  and  wheel 

304 

Railroad  engineering 

11 

drag 

304 

construction    and    maintenance, 

four-wheel 

308 

work  of 

11 

Fresno 

305 

economics 

213 

two-wheel 

306 

Note. — For  page  numbers  see  foot  of  pages. 


455 


INDEX 


Page 

Page 

Signaling 

179 

Switches                                                    146 

systems 

179 

construction                                      146 

automatic 

184 

frogs                                           149 

controlled  manual 

183 

guard  rails                                  148 

details,  mechanical 

186 

switch  stands                             148 

electro-pneumatic 

crossings                                     170-172 

semophores,  electric 

194 

crossovers                                   162,  163 

simple  manual 

180 

curve  connections                     159, 160 

wires  and  pipes 

191 

laying,  rules  for                                 167 

Simple  curves 

26 

slip                                                     168 

deflections,  computing 

31 

turnouts                                     155,  157 

deflections,  location  of  points 

by     30 

Switch  stands                                           148 

elements 

28 

instrumental  work 

32 

T 

length 

28 

Tables 

location,  modifications  of 

38 

Austin  trench  excavators,  sizes 

location,  obstacles  to 

35 

and  capacities  of              421 

location,  special  methods  of 

33 

cut-off  and  pounds  of  steam  per 

measurement,  method  of 

26 

1  h.p.-hour  for  various 

1°  curve,  elements  of 

29 

multiples  of  M                 269 

sub-chords 

27 

evaporation  in  locomotive  boil- 

Slip switches 

168 

ers,  average                      266 

Spikes 

136 

expenses,  operating                          224 

Stationary  scraper  excavator 

344 

expenses  of  railroads  in  U.   S., 

Steam  shovels 

operating                  226,  227 

fixed-platform 

318 

fixed-platform    shovel,    working 

arrangement 

318 

hmits  of                             325 

body,  car 

321 

head  velocity  of  trains                    244 

equipment,  excavating 

321 

motors    for    shovel    capacities, 

equipment,  power 

321 

sizes  of                               340 

operation,  cost  of 

327 

operating  a  train  1  mile,  average 

operation,  method  of 

323 

cost  of                                225 

revolving-platform 

332 

resistance,  locomotive                     270 

arrangement 

332 

standard  steam  shovel,  sizes  of     320 

equipment,  excavating 

334 

steam  shovel  service                        328 

equipment,  power 

333 

steam  used  locomotive  cylinders, 

operation,  method  of 

335 

weight  of                           268 

platforms 

332 

various  grades,  values  of  C-^  (72+ 

Stringers 

103 

K)                                    258 

Subaqueous  rock  breakers 

408 

various  multiples  of  M,  cylinder 

boat,  drill 

409 

tractive  power  of              272 

Lobnitz 

408 

wheel  excavators,  dimensions  of    364 

Surveys 

Templet  excavator                                  358 

location 

24 

Ties                                                           127 

preliminary 

19 

cost                                                    129 

railroad 

11 

cutting                                               129 

reconnoissance 

12 

dimensions                                        128 

Note. — For  page  numbers  »ee  foot  of  pages. 


456 


INDEX 


Page 


Page 


'lies  (continued) 

Trench  excavators  (continued) 

laying  and  reviewing 

129 

pipe-trench 

414 

spacing 

128 

tile-trench 

434 

wood 

127 

Trestles 

97 

Tile-trench  excavators 

434 

floor  systems 

103 

ditcher,  Hoveland  tile 

435 

framed 

100 

Tower  cableway  excavator 

430 

pile 

97 

Tower  excavator 

367 

Trestle  cable  excavator 

424 

Track  and  track  work  materials 

124 

Trestle  floor  systems 

103 

ballast 

124 

corbels 

104 

bolts,  track 

138 

fire,  protection  against 

108 

braces,  rail 

136 

guard  rails 

105 

joints,  rail 

133 

stringers 

103 

nut  locks 

138 

super-elevation  of  outer  rail 

on 

rails 

130 

curves 

106 

spikes 

136 

ties,  trestle 

106 

ties 

127 

timber,  choice  of 

109 

tie  plates 

135 

Tunnel  construction 

95 

Track  bolts 

138 

general  principles 

95 

Track  laying 

140 

methods 

96 

ballast 

140 

Tunnel  design 

92 

outer  rail  on  curves,  super-eleva- 

cross-sections 

92 

tion  of 

144 

grade 

92 

practical  rules 

145 

lining 

93 

rails 

141 

portals 

94 

surfacing 

144 

Tunnels,  surveying 

88 

surveying 

140 

character  of 

88 

ties 

140 

distance 

89 

Track  maintenance 

197 

down  shafts 

91 

ballast 

205 

levels 

89 

ditching 

202 

underground 

90 

labor,  or  organization  of 

209 

surface 

89 

rails,  distributing 

204 

Turnouts                                           155,  157 

ties,  distributing 

203 

Turntables 

118 

tools 

197 

trestle  filling 

207 

V 

work  trains 

201 

Vertical  curves 

57 

Track  trestle  excavator 

427 

geometrical  form 

58 

Transition  curves 

43 

use 

57 

compound  curves,  use  with 

53 

Volume  of  earthwork,  computing 

66 

deflections 

46 

borrow  pits 

77 

field  work 

56 

center  of  gravity,  eccentricity 

of     79 

spirals  in  old  track,  inspection  of 

50 

correction,  prismoidal 

75 

symbols 

46 

curvature,  correction  for 

78 

systems 

43 

irregular  ground,  volume  in 

75 

Traveling  derrick  excavator 

414 

methods,  common 

66 

Trench  excavators 

412 

prismoid,  volume  of 

68 

Note. — For  page  numbers  see  foot  of  pages. 


457 


INDEX 


Volume    of    earthwork,    computing 

(continued) 
products,  computation  of 
sections,  equivalent 
sections,  irregular 
sections,  level 
sections,  three-level 
side-hill  section,  eccentricity  of 

center  of  gravity  of 
side-hill  work 


W 

Walking  drag-line  excavator 
Walking  scoop  dredges 

Note. — For  -page  numbers  see  foot  of  pages. 


Page 


Page 


Water-supply 

115 

pumping 

116 

72 

tanks 

117 

67 

track  tanks 

117 

73 

Wheel  excavator 

362 

66 

69 

Y 

82 

Yards  and  terminals 

173 

77 

freight-yard   with 

main 

tracks, 

connection  of 

176 

proper  design,  value  of 

146 

573 

yards,  engine 

178 

J70 

yards,  freight 

174 

458 


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